Thorn Cycles Forum

Technical => Transmission => Topic started by: anweald on August 20, 2009, 10:25:53 PM

Title: thorn chainguards
Post by: anweald on August 20, 2009, 10:25:53 PM
Anyone know the exact dimensions of the Thorn chainguards esp the one for PCD 104mm for 44t rings? Also its weight and how it manages to not get in the way of the chain.

I'm really only wanting a trouser-hem-saver but those plastic chainring attachments don't seem available to buy separately. maybe they're not as light as they look anyway.
Title: Re: thorn chainguards
Post by: pyjamas on November 17, 2014, 10:17:28 PM
I saw an elderly lady with one of those very upright bicycles: when she was holding the bike, the handlebars were up near her chest.  She had hub gears, obviously, and a fully enclosed chainguard.  What struck me was that a Rohloff hub gear should also be suitable for a chainguard, which should go a long way to protecting the chain from wear.  Has Thorn ever considered this, or ever fitted Rohloff bikes with chainguards?
Title: Re: thorn chainguards
Post by: JimK on November 17, 2014, 10:21:40 PM
Here is my big clever idea:

I think a big problem with chain guards is that fitting them is very tricky. They need to hook onto or clear so many surfaces... maybe a perfect application for 3-d printing!?
Title: Re: thorn chainguards
Post by: il padrone on November 17, 2014, 11:04:27 PM
A number of people on here use and recommend the Hebie Chainglider. There is one made specifically for the Rohloff hub. These are lighter plastic guards that do not need frame fittings. I have one that will go on the bike when the current drivetrain wears out. Note: the Thorn double-sided chainring does not run with the Hebie, it's too wide and causes friction. Use a thinner alloy or steel ring.
Title: Re: thorn chainguards
Post by: John Saxby on November 17, 2014, 11:22:38 PM
+1 for the Hebie Chainglider, in my case fitted to my Raven with a 38 x 17 ratio.

Beyond the various Hebie products, however, there's a huge range of possibilities here:  http://www.dutchbikebits.com/index.php?route=product/category&path=43
Title: Re: thorn chainguards
Post by: Andre Jute on November 18, 2014, 03:53:33 AM
I saw an elderly lady with one of those very upright bicycles: when she was holding the bike, the handlebars were up near her chest.  She had hub gears, obviously, and a fully enclosed chainguard.  What struck me was that a Rohloff hub gear should also be suitable for a chainguard, which should go a long way to protecting the chain from wear.  Has Thorn ever considered this, or ever fitted Rohloff bikes with chainguards?

Try these threads:
http://www.thorncycles.co.uk/forums/index.php?topic=2233.0
http://www.thorncycles.co.uk/forums/index.php?topic=3561.msg15501#msg15501
http://www.thorncycles.co.uk/forums/index.php?topic=6813.0
http://www.thorncycles.co.uk/forums/index.php?topic=2480.0
Title: Re: thorn chainguards
Post by: pyjamas on November 26, 2014, 09:46:59 PM
Many thanks for all these responses: a lot for me to work on.
Title: Re: thorn chainguards
Post by: Matt2matt2002 on November 26, 2014, 11:11:22 PM
I'll second the Chain glider.
I've had it on a month, done 100 miles, so still braking it in so to speak.
But being early days I have paid extra attention for new noise and can hear none at all.
It may be a rash statement but I feel the Raven glides along even quieter than before fitting it.
Title: Re: thorn chainguards
Post by: phopwood on November 27, 2014, 10:19:16 AM
I fitted one about a month ago it needed trimming to fit my RST, but I have a thorn alloy ring which is very wide and it took a lot trimming around the edge where it was touching the ring.

I should have brought a thinner ring.  It still rubs in places as I can hear it, but I am sure it will break in eventually, or I will take it apart and adjust it's expectations with a stanley knife  ;D  That said I don't feel like it drags or adds much friction.

All the best.

Peter
Title: Re: thorn chainguards
Post by: in4 on November 27, 2014, 10:44:05 AM
Anyone have a preference re bashguards?
Title: Re: thorn chainguards
Post by: John Saxby on November 27, 2014, 05:59:44 PM
Quote
I feel the Raven glides along even quieter than before fitting it.

Matt, glad to know you've had such good luck with the 'glider.  Last week, I took mine apart after this first season (May to November, about 3,000 kms) and the chain is quite clean -- some dust, no grit at all.  I cleaned it anyway, as much out of habit as anything.

I'm going to try fitting the 'glider a fraction looser next spring -- mating the front and rear parts one more marker-notch apart, assuming I have enough fore-and-aft clearance around the front sprocket to do so.  Like you, I hear no noise, or very little. Wiggling the front end, I'd like a bit more play there. This may be just fussing though, enforced winter idleness.
Title: Re: thorn chainguards
Post by: Danneaux on November 27, 2014, 07:08:05 PM
Quote
Anyone have a preference re bashguards?
Hi Ian!

In the past, I made my own bashguards out of aluminum plate (complicated!) or (much easier!) by milling the teeth off a chainring 6T larger than the one I wanted to cover, then mounting using longer chainring spacers, bolts, and sleeve nuts (pegs). Now they're widely available for purchase (easiest of all!), but you still have to come up with the specifics for mounting.

[Same setup works for quad chainrings -- I managed five, once, back in the day -- provided you're willing to modify the front derailleur parallelogram and build up the shift lever's cable windup barrel so it'll span the gap and shift the range. The resulting bad chainlines limited the usable combinations and made it not worth the trouble. 'Turned out if you wanted really low gears, it was better to repurpose chainrings as freewheel cogs and mill a new cage for the rear mech, then combine that with a small chainring made from a cog. I found an 11 gear-inch low was about my limit before spin-out on 24% grades.]

I used a BBG (Bicycle Bash Guard) on Sherpa, pictured here: http://www.thorncycles.co.uk/forums/index.php?action=dlattach;topic=3896.0;attach=1036;image
Available here: http://www.bbgbashguard.com/Mountainbike.html
Fitting details here: http://www.thorncycles.co.uk/forums/index.php?topic=3821.msg16591#msg16591
Sherpa's was fitted primarily to protect *me*...the wounds caused by an "open" large ramped chainring can be brutal. For those with a strong stomach, see: https://www.google.com/search?q=chainring+injury&biw=1280&bih=713&source=lnms&tbm=isch&sa=X&ei=s2V3VLuKFsblau7zgqgO&ved=0CAcQ_AUoAg

For Seymour the Nomad, I've been very pleased with Thorn's offerings. Versions are available for 5-arm and 4-arm cranks and different BCDs and sized for a range of 'ring diameters.

The bash guard fitted to the Nomad was primarily to prevent chain oil transferring to my calf. Nothing removes chain oil deposits from cycle-tourists' legs better than the interior of a nice down sleeping bag or silk liner! Best to prevent them happening in the first place.

Thorn's 4-arm bash guard shown installed here: http://www.thorncycles.co.uk/forums/index.php?action=dlattach;topic=4523.0;attach=4421;image
Available here: http://www.sjscycles.co.uk/find.asp?site=&name=thorn&page=1&geoc=US#filterkey=cat&cat=504&page=1

Please be aware, fitting a bash guard to a derailleur drivetrain's triple chainset will require spacers and longer chainring bolts/pegs, as detailed in the third link above. If fitted to a Rohloff-equipped bike, the bash guard can be spaced outside a chainring mounted in the outer position on the crank spider, or the chainring may be moved to the inner position and the bash guard fitted like an outer chainring with longer bolts and sleeve nuts after adjusting the chainline (what I did).

Please note: I would fit a Hebie Chainglider, but they are not currently made to accommodate my 36x17 gearing, which I prefer.

Best,

Dan. (...who is usually "on guard" against mishaps)
Title: Re: thorn chainguards
Post by: Andre Jute on November 27, 2014, 10:46:24 PM
I'm going to try fitting the 'glider a fraction looser next spring -- mating the front and rear parts one more marker-notch apart, assuming I have enough fore-and-aft clearance around the front sprocket to do so.  .... Wiggling the front end, I'd like a bit more play there. This may be just fussing though, enforced winter idleness.

My granny used to say, "Idle hands are the devil's ear cushion." Don't ask me; I just report the facts accurately.

But in this case, perhaps not so idle. If a Chainglider is fitted so tightly that there is no movement, I definitely think it is too tight. I have a moment of pause for thought here, because you say it isn't noisy. In my experience, a correctly fitted Chainglider can be easily selected because it is the least noisy fitment, but mine is so silent at all points of adjustment that it is a very subtle judgement. I think there should be between 3mm and 6mm of movement. But the adjustment is pretty crude, so that depending on your chain length adjustment (EBB, sliders, whatever), you could end up with 2-7mm of play and that will be still be good. I tried the Chainglider loose enough to show more than half an inch of movement, and that was definitely audible, more as banging and wind noise than as rubbing though.

I wasn't happy with Chainglider adjusted down to about 1mm and less of movement, ie tight. It was almost imperceptibly noisier, possibly (I'm tempted to say probably) a fraction draggier, just didn't feel right in the ride.

There is so much anecdotal evidence now about clean insides on Chaingliders with 3K+ of use, I'm starting to wonder what magic plastic the thing is made from. And whether it actually "glides" on the chain, or on some thin layer of air.
Title: Re: thorn chainguards
Post by: mickeg on November 28, 2014, 12:49:34 AM
Anyone have a preference re bashguards?

Yes.  I did something similar to Dan, I bought a cheap 52T chainring on sale.  Cut the teeth off of it with a saber saw.  It ruined the saw blade, the Aluminum clogged up the teeth on the blade.  Then I installed it in the outer position on my double crankarms, I use the inner position for my 44t chainring.  I used a file to file off the cut marks, held the file against the chainring while I turned the pedal by hand.  See photo.

Since I have a Rohloff, I only need one chainring.  Around home I only have one chainring on the bike, but if I take the bike on a tour I expect to have two chainrings on the bike so I can add or subract a few chain links to switch to the other chainring if I need higher or lower gearing, for that I would not bother with a bashguard.
Title: Re: thorn chainguards
Post by: Danneaux on November 28, 2014, 03:23:17 AM
Quote
It ruined the saw blade, the Aluminum clogged up the teeth on the blade.
Careful selection of tooth count, a slow cutting speed and slow feed speed with kneaded beeswax as a cutting lubricant rubbed into the teeth helps tremendously to prevent blade clogging.

Alternatively, the teeth can be nipped off with an end-cutter or chop-saw, then smoothed down against a grinder before edge-milling.

Yours looks really nice, Mickeg!

Best,

Dan.
Title: Re: thorn chainguards
Post by: Danneaux on November 28, 2014, 03:26:49 AM
Quote
There is so much anecdotal evidence now about clean insides on Chaingliders with 3K+ of use, I'm starting to wonder what magice plastic the thing is made from. And whether it actually "glides" on the chain, or on some thin layer of air.
Andre,

Hebie's representative advised me to use a thin coating of light grease on the chain to minimize friction and noise inside the Chainglider (don't have one on my needed size, so I haven't tried this). I'm guessing the factory lube on a fresh chain is very close to a light grease for this purpose and accomplishes the same end. Thin grease might be worth trying for those who clean their chains in a solvent tank and then wish to recapture the "quiet effect" inside a Chainglider.

Best,

Dan.
Title: Re: thorn chainguards
Post by: John Saxby on November 28, 2014, 04:01:38 AM
Quote
I think there should be between 3mm and 6mm of movement.

Thanks for your well-advised note of caution, Andre.  You're the village elder in these matters--strictly from the POV of 'glider experience & wisdom, to be sure :-)  -- so I'll take note of your suggested 3 - 6 mm of play.  I've disassembled my 'glider for cleaning, so will try to be a bit more precise than just "wiggling" my chainring case when I reassemble it all.

PS on the matter of being an elder statesman:  You could be an experienced fundi rather than an mzee, if you wish. either one's a pretty good State of Being, I reckon.  I was grumbling a little while ago, on a skype with our daughter, about some major irritant, probably some SUV driver trying to kill me, I can't recall, and she said, knowing what the Proper Order of Things is in Africa, "Dad, you're an mzee now--you don't need this kind of thing."
Title: Re: thorn chainguards
Post by: Andre Jute on November 28, 2014, 06:55:33 AM
I'm golden, John, definitely golden. Fundi! Love you too, man.

I like Mick and Dan's bash guards; they are aesthetically so much more pleasing than anything one can buy.

Dan, the representative of Hebie by the nature of his job must master a large, diverse catalogue of stuff. His refusal to believe something that Rolloff published on their own site after you told him of it persuades me that he hasn't yet found time to master the Chainglider. Until he does, I have no hesitation in believing I know more about it than he does, and, anyway, in general, I would on most subjects prefer the collected wisdom, experience and common sense on this forum to the dicta of someone junior and young enough to be answering emails for a great manufacturer and distributor. Returning to the Chainglider's innards, experience in use shows me no need whatsoever of additional grease or oil inside the Chainglider, and when I do, if ever, add anything I intend trying a stingy few dropa of Oil of Rolloff, a chain lubricant I've found very, very good before, and I'll be putting it on the chain, not on the surface of the Chainglider, which I can see and hear doesn't need assistance. Of course, when one of us hears from these people, it is good to share, so I don't want to discourage you; but I hope you'll take no offense when I say I attach higher credibility to the information you extracted from the engineer's desk (via his wife, i seem to recall) at Tout Terrain.
Title: Re: thorn chainguards
Post by: Danneaux on November 28, 2014, 07:22:20 AM
Congratulations on your attainment of Superhero status (2,000 posts), Andre.

Best,

Dan.
Title: Re: thorn chainguards
Post by: Andre Jute on November 28, 2014, 07:31:29 AM
Congratulations on your attainment of Superhero status (2,000 posts), Andre.

Good heavens! I hadn't noticed. Thanks, Dan.
Title: Re: thorn chainguards
Post by: John Saxby on November 28, 2014, 10:10:46 PM
Quote
Good heavens! I hadn't noticed.

The numbers just tick over unnoticed when you're having fun, Andre.  Well done!  :-)
Title: Re: thorn chainguards
Post by: Slammin Sammy on November 29, 2014, 06:10:12 PM
Congrats, Andre! A truly Herculean effort - nearly an order of magnitude more posts than I.  :)

Dan, this probably calls for a new thread, doncha think?

And just watch out when you see him entering a phone box. You know the mild mannered, erudite Andre Jute is transforming into... Superhero Andre!

Whew!  :D ;)
Title: Re: thorn chainguards
Post by: Andre Jute on November 30, 2014, 12:29:26 AM
"Superhero" sounds a bit like I'll be wearing my underjocks over my trousers from now on... The cost of fame is dignity.

Here's a superhero novel, written by Dakota Franklin, Andrew McCoy and me, that y'all can download free of charge in any format you want — click the link or the cover:

Gauntlet Run: Birth of a Superhero (http://www.smashwords.com/books/view/409600)

(http://cache.smashwire.com/bookCovers/76c7e8a328b5db289746da881c6caef4e1f350ea) (http://www.smashwords.com/books/view/409600)
Title: Re: thorn chainguards
Post by: JimK on November 30, 2014, 02:53:34 AM
Hey this is non-stop action for sure! But even better - I was just driving north on US-206 past I-78 just about a week ago! Netcong!

... and quoting Jacques Ellul! Too much!
Title: Re: thorn chainguards
Post by: Andre Jute on November 30, 2014, 01:01:50 PM
Hey this is non-stop action for sure! But even better - I was just driving north on US-206 past I-78 just about a week ago! Netcong!

... and quoting Jacques Ellul! Too much!

You'll enjoy this. The borough motto of Netcong is:
All roads lead to Netcong.

Honest. Makes you wonder what the cycling is like.
Title: Re: thorn chainguards
Post by: JimK on November 30, 2014, 03:37:10 PM
That was my first time up in that little corner of New Jersey. I had gone down to Princeton to sell some books & figured I might as well do a little exploring on the way back so I hiked a bit of the Columbia Rail Trail, starting in Long Valley. I've been in some obscure parts of New Jersey before, but Netcong definitely qualifies!

But it is easy to sympathize. They're a tiny village. Not only does I-80 go through, which... I was going through around 6PM on a Sunday. I guess it was folks going back to the city after their weekend in the Poconos, but the road is like 5 lanes wide and just jammed with cars speeding and dodging between lanes... I was heading east to pick up I-287 and get back home. Anyway beyond I-80, US 206 and US 46 go through there. That little village is like a mega-interchange. They're tucked into a little valley. The sound of the traffic, all night long! I can see how it might feel like "All roads lead through Netcong!" I guess the official version is more poetic or something.
Title: Re: thorn chainguards
Post by: julio on November 04, 2017, 07:12:09 PM
Hi all,

I'm planning to buy a alloy chainguard like this one
https://www.sjscycles.co.uk/chainsets/thorn-high-quality-alloy-chainguard-for-110-pcd-rings-up-to-38t-black/

Acutally my chainring is an 40 teeth, but my next will certainly have 38 teeth.. someone can advise me which chainguard size do i need ?

As well, can i reuse my chainring bolt ?
Title: Re: thorn chainguards
Post by: mickeg on November 04, 2017, 11:00:03 PM
Hi all,

I'm planning to buy a alloy chainguard like this one
https://www.sjscycles.co.uk/chainsets/thorn-high-quality-alloy-chainguard-for-110-pcd-rings-up-to-38t-black/

Acutally my chainring is an 40 teeth, but my next will certainly have 38 teeth.. someone can advise me which chainguard size do i need ?

As well, can i reuse my chainring bolt ?

Did you read this (which I pasted here from the SJS link that you posted):

   Details
   This chainguard fits in place of an outer chainring on a double/triple, can be made to fit as well as three rings by using longer
   bolts and  4.6mm spacers if the crank has enough space between the arm and the outer ring. If in doubt ring for advice.


So, do you plan to remove one chain ring and install that instead?  If so, you can re-use your chainring bolts.
Title: Re: thorn chainguards
Post by: julio on November 05, 2017, 04:05:27 PM
Ok but i don't want to change my chainring now, so i don't know if i can use a chainguard up to 38 t with my actual chainring 40 t .. ?    :-\
Title: Re: thorn chainguards
Post by: martinf on November 05, 2017, 07:20:14 PM
You didn't say what you wanted the chainguard for:

1 keeping trousers or legs clean
2 stopping the chain jumping off the chainring (IMO very unlikely with a Rohloff)
3 as a bashguard to protect the chainring from rocks

For 1, the Hebie Chainglider works OK, and also protects the chain, in my experience prolonging chain life and reducing the need to clean chainring/sprocket and chain.
The Chainglider works best with a narrow chainring like the Surly stainless steel. And only with some combinations - AFAIK 40T doesn't work, but 38T x 16T and 38T x 17T do work.
I don't think the Chainglider will work well as a bashguard.

For 2, I used an old chainring with the teeth cut off and filed smooth. This worked with a single chainring and rear derailleur. It would probably have worked with the teeth still on, but looked better without. Mine was 4 teeth bigger than the chainring.

For 3, an old chainring several teeth bigger should work (I reckon at least 6), or a purpose made chainguard like the Thorn. I may be wrong, but I think the one designed for a 38T ring would be too small to properly protect a 40T ring.

To fit a Thorn chainguard to a Rohloff bike, the best way is probably to get a longer bottom bracket axle, double chainring bolts rather than single, fit the chainguard in the outer position and the chainring in the inner position. If you have enough space between crank and chainring you might be able to fit the chainguard outboard of the chainring, so just need spacers and double or triple chainring bolts.
Title: Re: thorn chainguards
Post by: PH on November 05, 2017, 07:24:40 PM
EDIT - Part duplicated what martinf was typing at the same time, but different enough not to bother changing...

Ok but i don't want to change my chainring now, so i don't know if i can use a chainguard up to 38 t with my actual chainring 40 t .. ?    :-\

Most probably not, the maximum T size will have the chain running just below the edge, the guard would at best be pointless if the chain was above the guard and if this wasn't the case with 40T it's hard to imagine why it wouldn't be advertised as such.
Chainring bolts - if you're currently running a single chainring in the outer position, you'll need to move it to in middle/inner position and put the guard where the chainring is now, this will need double bolts rather than the single you most likely have now. 
Also consider doing the above changes the chainline, if you wish to maintain the current one, you'll also need a different bottom bracket.
Title: Re: thorn chainguards
Post by: Danneaux on November 05, 2017, 07:32:49 PM
Agreed with Martin; when I make my own bash guards, I do so by filing the teeth from old chainring that are 6 teeth larger than the 'ring I am trying to protect.

The experiences related by others in this thread matches my own.

All the best, Julien,

Dan.
Title: Re: thorn chainguards
Post by: mickeg on November 05, 2017, 09:07:49 PM
It is not clear to me if this is for a Rohloff bike or derailleur bike with a double/triple? 

And if it is for a Rohloff bike, does it have a double crank? 

And if it is a double with one chainring on a Rohloff bike, do the chainring bolts have the little spacers that come with the Rohloff that allow you to use the double length bolts with a single chainring on a double crank?

In other words, we can't make firm answers without knowing what the situation is.

For my Nomad (Rohloff) bike which has a double crank, I cut the teeth off a 52T chainring to use as a bashguard with a 44T chainring, thus 8 teeth difference.  That was a bit bigger than it needed to be but it was functional so that is what I use. 

Touring where I use a 36T chainring on the inner position on a double crank, I use a 44T chainring as a bashguard because if I conclude that the 36 is too low, I can add a few links to the chain and use the 44 instead.  But it looks a bit odd to have two chainrings and no front derailleur.

If you have a chainring in the outer position on a Rohloff bike and move that chainring to an inner position, that will change your chainline a bit.  My chainline is off about 5mm because I run my chain on a chainring on the inner postion, but my chainline would be perfect if I had the chainring in the outer position.  I see a 5mm out of line position as not a problem, but I have no clue what you have on your bike.
Title: Re: thorn chainguards
Post by: PH on November 06, 2017, 01:08:41 AM
It is not clear to me if this is for a Rohloff bike or derailleur bike with a double/triple? 

Well, the question is based on a single chainring...
Given that I doubt it matters whats on the back, IGH, SS, 1X
Title: Re: thorn chainguards
Post by: julio on November 06, 2017, 03:22:40 PM
You didn't say what you wanted the chainguard for:

1 keeping trousers or legs clean
2 stopping the chain jumping off the chainring (IMO very unlikely with a Rohloff)
3 as a bashguard to protect the chainring from rocks

I sent this link in my precedent message ..
https://www.sjscycles.co.uk/chainsets/thorn-high-quality-alloy-chainguard-for-110-pcd-rings-up-to-38t-black/

But thanks for these responses. I would like this chainguard firstly to protect trousers

I've only one bike, it's a Nomad with rohloff
(https://i62.servimg.com/u/f62/19/07/93/69/th/p1100912.jpg) (https://servimg.com/view/19079369/208)

:) thanks
Title: Re: thorn chainguards
Post by: julio on March 05, 2018, 01:07:47 PM
Sorry i reiterate my question..

Can i use this Thorn chainguard (up to 38 teeth) with my future Surly chainring 36 t ?

https://www.sjscycles.co.uk/chainsets/thorn-high-quality-alloy-chainguard-for-110-pcd-rings-up-to-38t-black/

Title: Re: thorn chainguards
Post by: martinf on March 05, 2018, 04:24:22 PM
If it works for 38T it will work for 36T
Title: Re: thorn chainguards
Post by: julio on March 05, 2018, 09:58:50 PM
Ok Martin ..

But i noticed one thing.. if i add a chainguard, my chainring will take the inner position and it will touch my plastique bottle   >:(

(https://i62.servimg.com/u/f62/19/07/93/69/th/img_2016.jpg) (https://servimg.com/view/19079369/217)

Also, to have a chain misaligned i'am not a fan, so maybe i'll add just spacers and basta  8)
Title: Re: thorn chainguards
Post by: martinf on March 05, 2018, 10:40:05 PM
If you want to fit the chainguard where the chainring currently sits, and the chainring inside of this, the best way is to fit a longer bottom bracket unit (boîtier de pédalier). If you choose the right length, you should be able to get the chainline correct (and not touch the bottle!).

If there is enough room between crank and chainring, cheaper would be to keep the chainring in the current position and use longer chainring bolts and spacers to fit the chainguard outboard of the chainring (closer to the crank).
Title: Re: thorn chainguards
Post by: John Saxby on March 05, 2018, 11:09:25 PM
Julio, if you're using a 36T or 38T chain ring, you could fit a Hebie Chainglider as a chainguard, without altering your chainline.

The Chainglider for the 38T ring will fit a 36T ring--I have one on my Raven. You have to cut out one part of the Chainglider, the piece covering the rear of the chainring, but it still works well. 

If you think that would be useful, I can send you a photo of the Chainglider on my Raven.

Cheers, John
Title: Re: thorn chainguards
Post by: julio on March 06, 2018, 06:58:33 PM
If you want to fit the chainguard where the chainring currently sits, and the chainring inside of this, the best way is to fit a longer bottom bracket unit (boîtier de pédalier). If you choose the right length, you should be able to get the chainline correct (and not touch the bottle!).

If there is enough room between crank and chainring, cheaper would be to keep the chainring in the current position and use longer chainring bolts and spacers to fit the chainguard outboard of the chainring (closer to the crank).

So it isn't obligatory to put my Surly chainring in the inner position ? (if i want to add a Thorn bashguard)

But how can i mesure if i have enought room between crank and chainring ?

John, maybe another day about to install a Chainglider, however i'm afraid to hear noise and also i like to see my chain  :)
Title: Re: thorn chainguards
Post by: mickeg on March 06, 2018, 07:51:53 PM
...
But i noticed one thing.. if i add a chainguard, my chainring will take the inner position and it will touch my plastique bottle   >:(
...

If you bottle cage is one that can't be bent a bit to the side, buy a different cage that can.

If the cage is robust and hard to bend, take it off the bike and bend in a vice to avoid damaging the cage bolt fittings on the frame.
Title: Re: thorn chainguards
Post by: martinf on March 06, 2018, 10:07:34 PM
So it isn't obligatory to put my Surly chainring in the inner position ? (if i want to add a Thorn bashguard)

But how can i mesure if i have enought room between crank and chainring ?

No, you can fit the bashguard outboard.

You need the gap between the edge of the chain and the crank to be wider than the bashguard, ideally at least width of bashguard plus 2 mm each side to allow clearance between bashguard and chain and bashguard and crank.

I ran a chainguard outboard of the chainring on an old TA crankset with a single ring and rear derailleur gears to prevent the chain unshipping when shifting.

Old TA has a narrow gap compared with most modern cranks, but the chainguard wasn't very wide either.
Title: Re: thorn chainguards
Post by: julio on March 06, 2018, 10:49:36 PM
Ok fine.

So maybe i'll need to play with spacers to adjust clearance ..

I receive my Surly chainring soon, i will see better once at home, but i have not ordered yet the bashguard, i'm afraid not being able to install it. 
Title: Re: thorn chainguards
Post by: martinf on March 07, 2018, 07:58:58 AM
So maybe i'll need to play with spacers to adjust clearance ..

Probably. In the past I have sometimes filed down the aluminium alloy spacers on old TA chainsets to reduce the gap between 2 chainrings (for example to fit a triple on a fairly short bottom bracket axle or to improve shifting and chainline for the large and middle rings on a half-step triple).

Another possibility is to use a stack of washers instead of the spacers, done this to fit a chainguard outboard of a single chainring on a 5-arm crankset.

You will probably also need longer chainring bolts.
Title: Re: thorn chainguards
Post by: julio on March 12, 2018, 10:27:36 PM
As you see, the chain touches the bashguard (i can't slip in a sheet of cigarette paper between)

(https://i62.servimg.com/u/f62/19/07/93/69/th/img_2022.jpg) (https://servimg.com/view/19079369/225)

However, i used 2mm aluminium spacers but it's not enought .. 3mm would have been fine i think.

So can i add a stainless steel spacers that i have at home ?

(https://i62.servimg.com/u/f62/19/07/93/69/th/img_2023.jpg) (https://servimg.com/view/19079369/226)

On these 2 pics, can you tell me if it seems ok ?

(https://i62.servimg.com/u/f62/19/07/93/69/th/img_2024.jpg) (https://servimg.com/view/19079369/227)

(https://i62.servimg.com/u/f62/19/07/93/69/th/img_2025.jpg) (https://servimg.com/view/19079369/228)
Title: Re: thorn chainguards
Post by: martinf on March 12, 2018, 11:12:57 PM
However, i used 2mm aluminium spacers but it's not enought .. 3mm would have been fine i think.
So can i add a stainless steel spacers that i have at home ?

Yes. Done this. If one per chainring bolt isn't enough, use two.

On these 2 pics, can you tell me if it seems ok ?

I think you probably need longer chainring bolts - after adding the stainless steel spacers there doesn't seem to be much thread left holding the bolt into the nut.
Title: Re: thorn chainguards
Post by: julio on March 23, 2018, 10:56:03 AM
So difficult to find the right length chainring bolts .. so currently my bolts stop at the middle of the thread (see pics)

(https://i62.servimg.com/u/f62/19/07/93/69/th/img_2025.jpg) (https://servimg.com/view/19079369/228)

About the nuts, they supporte the crank, the Surly chainring and half of my spacers so 1.5 mm (on 3mm)

The right length  will be : Bolts  :  9mm (under head)
                                     Nuts   :  10 mm   (  "  )