Thorn Cycles Forum
Technical => Wheels, Tyres and Brakes => Topic started by: paulhipwood on December 28, 2006, 03:44:16 pm
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Hi All
Have just washed my bike and noticed that there are many cracks at the nipples - about 15 of the 32 nipples holes have cracks - these generally are radial along the rim and about 10 mm long. The wheel is still running true and the spokes feel at the correct tension.
I have done about 3000 miles on this rim, I bought the bike second hand and it had done about 1000 miles by the other owner.
The rim is a Mavic 717 and I use Schwalbe Marathon plus 1.3 (smartguard) at 80 psi. Have never had a puncture and never run with low pressure.
I have not noticed these before and usually wash the bike every couple of weeks.
I use the bike for commuting and Sunday runs. I ride along the canal during my commute.
I am about 85 kg and carry no more than 10 kg in the rear panniers.
Has anyone else had this problem and what do you think has caused the cracks?
What would you recomend as a replacement?
best regards
paul
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http://aolpictures.aol.co.uk/galleries/paulhipwood
Thought I would put these on to illustrate the cracks.
Sorry about the aol adverts!!!!
regards
paul
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Not Good,
After reading about your problems I went to check my rims. I've got 4 mavic rims, 2 * 717, 1 * 717 ceramic and 1 * 517? Ceranic. All rims are 32 hole. I have always being an advocate for mavic rims however the 517 rim (ceramic - rear) is cracked badly. It has got about 6000 miles on it. Luckily all my other mavic rims (717s) are fine - they have varying mileage of up to 4000 miles.
Oddly the wheel is still true (I put it in the stand to check! I use the bike mainly for commuting along with some UK touring (I am never very far from help). Therefor I am not planning to replace the rim any time soon.
As for what to replace it with – up until now I would have said another mavic. Don’t know what to advise any more.
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Oh dear, Mavic rims had a reputation for this, especially when the spoke tension was high. My LBS assured me it was in the past and I’ve recently had my rear rim replaced with the same 717. Just been to look and no cracks yet, though it’s only done around 2,000 miles.
As for replacements, the Sun CR18 I originally had was OK, I was a bit disappointed with how long it lasted, probably to be expected with a lightweight rim. On my old commuting hack, Rigida Sputniks lasted well and were cheap, they are a good bit heavier, not that I ever noticed.
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Hi all
The spokes are double butted and the cracks are from both sides of the hub.
I have checked the Rohlof manual and checked the lacing and it is correct for the nipple hole orientation.
I spoke to Thorn and told them of my problem. They said they had heard of this happening before with Mavic rims.
The bike is nearly three years old and there are to many unknowns with its history - honest I have never gone down a pot hole.
So I will get a new rim fitted, I will probably take it to Thorns and get them to fit it. They recommended a Sun CR18.
I am not too sure if any local bike shop has seen a Rohlof, so I do not want to risk it.
regards
paul
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Seven years ago I had the same problem but with a rear Mavic X517. At the time I was cycling over to Graz from London and only discovered the cracks when I washed the bike for the journey home! It turned out that I was carrying too much weight... well, it was my first tour and I didn't know any better!
In your situation, I very much doubt it should have happened unless the tension was too great in the first place, the rim was faulty, too much load was carried by previous owner or that it had taken too many pot holes. Maybe the previous owner did far more miles than stated, mine broke around 5000miles on the clock?
As for a replacement, the CR18's look like they'd last under touring conditions (I have only used mine for about 200Km... ask me in a years time!) but if you really want to stick with Mavics, XM719 look like they would do the job well - I replaced my cracked up X517's with the older equivalent D519's and they lasted me through some really tough situations until the side walls became so concave that I did not want to risk it any more!
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After doing a bit of research on the web it seams that 517 rims are very prone to this kind of cracking. (My failed rim is a 517.) I had heard of this problem before but I wanted confirmation. Mavic seams to give three excesses for this 1. Spoke tension is too high 2. Tyre pressure is too high 3. Carrying too much weight. There are far less reported problems on the 717 rim - however there are still too many for comfort.
I build my own wheels. Unfortunately I didn't build the 517 up (I bought it second hand) however I know that I did re-tension the wheel to 110psi ave spoke tension. I am sure that I would have spotted any cracking then - I didn't so the cracks have appeared in the last 4000 miles. (Of 6000.)
When I do eventually replace my 517 rim I am probably going to go for a DT Swiss 4.1 or possible a Mavic 717 (I am still hopeful and all my other 717 rims are fine). My third choice would be the Sun CR18.
I don’t have any experience of Sun or DT Swiss rims so my choice will be based solely on web reviews. My criteria may also be slightly different from yours, as most of my cycling is unloaded.
Best of luck with your new wheel.
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Hi Stutho
Are these front rims that you are quoting?
What are you using to check the tension?
Can you also check your units - 110 psi is a pressure not a load. Rohlof state that for a strong wheel the force should be a min of 700 N (aprox 70 kg), this is on page 41 of their manual.
I am seriously thinking of having a Sun Ryhno and ignore the extra weight.
regards
paul
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Hi Paul,
Rims I own: - 717 ceramic 32 hole front on a Hope hub - 4000 miles, condition - fine.
- 717 32 hole front on an XT hub - 2500 miles, condition - fine.
- 717 32 hole rear on XT hub 2000 miles condition - fine.
- 517 ceramic 32 hole rear on a Rohloff ~ 6000, miles condition - cracked.
- Bontrager 20 hole front 700c ~ 4500 miles, condition rim badly eroded.
- Bontrager 24 hole rear 700c ~ 4500 miles, condition rim badly eroded.
I use a park tools spoke tension meter to set the spoke tension. You are right about the units!! I should have said that I re-tension the wheel to 110Kgf or 1100N. A decent wheel build normally requires an average tension of above 1000N.
I am not a mechanical engineer but I am wondering if the spoke holes were de-burred before the eyelets were fitted. If the de-burring was skipped I believe it would lead to exactly the problem we are seeing.
Best of luck with the Suns
Stuart
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Hello,
I have two bikes with X517 rims. A Thorn Nomad and my Thorn Raven Tour. Funnily enough I have arriving today from SJSC a new rear wheel for the Nomad.The rerason being that I have a front wheel with hub dynamo fitted to Mavic X517 and the rear was looking odd as it was a Sun CR 17A.Now I will have a matching pair. I find that most rims last well with care. I have been aware of the cracking issue but admit that my own experience shows no problems.Having owned numerous bikes with varied rims I can say with all honesty that I have only had one rim break, and it was from hitting a road pothole!
I do not personally feel that people should worry too much about these rims as after all they have been/were selling in large numbers over a long time. Plus, if you were to look up statistics about any rim it would possibly show failures of this kind. In my opinion for what its worth, enjoy the ride and the ride will look after you.
John.
www.pbase.com/john28july
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Hi John,
Are you sure your Raven is using X517 rims? The reason I ask is that that particular rim has being off sale for well over a year (longer?). Maybe SJSC have a stock of them?
2 years ago I experienced a rim blow out (Pre Raven). I was lucky - of all the places it could of happened I was on holiday in Centre Parcs at the time. I was also lucky that it was the rear wheel, if it had being the front then I WOULD of gone over the bars. My 1 year old son was sitting in a child seat at the time, luckily he too was unhurt. I never want to test my luck that much again.
It was this incident that led me to learn how to build my own wheels. The wheel in question was at least 10 years old (on my hack bike) but wasn't looking bad . After the blow out 1/3 of the rim detached itself and jammed up the brake blocks. If I had ANY cracking in a front rim I would retire it immediately however the fault is in a rear. I am therefor going to watch and wait for the wheel to go out of true before I change it.
I like to think I look after my bikes, they all get very well used but I also get clean and maintained. I didn't spot the cracks until I looked for them and that’s a worry.
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Hello,
I had the rims as a spare set and had my Rohloff built into the rerar and Dynamo hub into the front.. I bought the rims last April whilst on a day out in Devon.My Raven Tour was built by mtself from a frame kit purchase. Good price too. I do know that the subject crops up from time to time about various rims failing. All I can really say is that this model rim is not alone, and that I have not had failure other than damage by potholes in road.
This is from a Internet Blog.
The German bike mag "BIKE" ran a test of lightweight MTB wheels for their latest issue [August 1999]. Most wheels (including Crossmax) failed quite a bit earlier than heavier "standard" wheels. Of more interest to us in this group: The test did confirm that X517 rims will develop cracks along the inner wall (i.e. under the rim strip - hard to detect for those of us using the beloved Velox rim strips).
Many riders have reported the same type of failure with the older 217-rim (which, except for the diameter and the fact that the T217 has double eyelets, is the same as the 700C T217).
Even more interesting: The Mavic engineer questioned about this remarked that the X517 is clearly to be considered a lightweight rim, suitable for light riders only (less than 75kg/165lbs). Which tandem team weighs less than 165lbs? Also, this rim should not be used with a tire pressure higher than 5bar (72.5psi according to Sheldon's online dictionary). This would render the rim useless for any road application with narrowish tires! This recommendation contradicts Mavic's own recommendation table shown below, which allows higher tire pressures for narrow tires. In any case you should probably be careful not to use these rims with extremely high tire pressure.
Now many riders have used these rims without problems on their road tandems, certainly running no less than 100-110psi, and the only problems reported have been loose ferrules. Still, should you have these rims on your bike stop riding immediately if the rim starts to bulge outward. With this type of failures the rim will become wider before it fails. This will usually lead to brake shudder. Failure will usually entail releasing the tire which could be disastrous if it happens on the front wheel. The two pictures show this type of failure. Failure will usually occur as you pump up your tire. You neigbors will check on you after hearing the loud BOOM the exploding tube makes, but will find you unharmed (except for slight hearing problems). However, as the tire could also come off the rim while you are riding, please do be careful. You will have to remove the rim strip to check your rim.
I have been riding Mavic rims with good results on almost all of my bikes since I started choosing my own components. I might prefer other rims in the U.S. due to Mavic's prohibitively high prices there.
You could look here too.
http://www.mtbr.com/reviews/olderwheelset/product_23666.shtml
Makes grim reading? Not really..........
John.
www.pbase.com/john28july
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An added thought.
Any rim will fail eventually. Thought given to use is of course important plus regular carried weight of rider (I am 74 kilos) and any luggage. My bikes are not used for heavy weighted luggage as all Camping equipment is of high specification and very lightweight (and expensive too!).My new Rear Wheel has just arrived so I am now off to fit it.Also of course the weather wrecks some rims, for instance heavy grit roads with mud and grime when wet do not help rims. But ultimately I would think that spoke tesion bears the brunt of the rims tension for the type of cracks mentioned.
John.
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This issue (of Mavs cracking on touring bikes) has come up again on Lonely Planet's forum ( here : http://thorntree.lonelyplanet.com/messagepost.cfm?postaction=reply&catid=32&threadid=1372467&messid=12042863&STARTPAGE=1&parentid=0&from=2 ) and the point was made that Mavic doesn't make rims specifically for touring. The EX721 ceramic that my Raven has is an MTB rim that appears to be rated for tyre pressures no greater than 49psi and fat tyres too. Yet Thorn recommended it to me and I saw a number of other bikes being built up in the shop with those rims. It was a top of the line rim and I obviously discussed with Thorn (I went to Bridgwater to choose the bike and all its kit) my intended use ('loaded touring on rough roads'). I was unaware at the time of the info on Mavic's site and didn't click on the 'technical information' buttons that would have showed the purpose and parameters of that rim.
I'm hoping one of the Thorn people might comment on why they stock or recommend the EX721 for touring. I've had no problems with mine, it's fairly young but had a hard 2000km in Tibet. I don't carry too much stuff, nor do I pump the tyres too hard, but I do use only 1.75" tyres, which appear to be narrower than Mavic intended for this rim.
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<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">1.75" tyres, which appear to be narrower than Mavic intended for this rim<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">That was my understanding too. It was a factor in me deciding to use 717 instead.
From the Mavic web site:
717(http://i139.photobucket.com/albums/q313/stutho/717.jpg)
EX721(http://i139.photobucket.com/albums/q313/stutho/EX721.jpg)
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That's it. So, freely admitting I'm a dummy for not looking into this further, but taking it on Thorn's recommendation, I'm curious why they do spec the EX721. I'll have to ask them if they don't surface soon on this thread.
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There is an interesting thread on the same subject (Mavic rims with Rohloff hubs) on www.tandem-club.co.uk on the discussion board which is searchable. This seems to indicate that Thorn may be starting to make available 40 hole rims with specially drilled Rohloff hubs for tandem use. Could also be useful on solos for heavily laden touring (or very large riders!)
David
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Thanks for this info Stuart. I am learning something new all the time here. I've 717 on my RST but didn't think about tyre size and tyre pressure when I specced them. I better make sure I don't go above 88psi.
By the way re slicks I've got some WTB Slickasorous 1.5" from LBS, JD Cycles in Ilkley. John the owner highly recommends them, £13 each.
I haven't put them on yet but will let you know how I get on.
Steve
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Well it's finally gone,
After about 12000 miles (10,000+ on the RST) my ceramic 517XC has finally died a spoke has pulled through. It has spoke hole cracking for at least the last 6000miles.
Now do I go and buy a 717XC ceramic (to match my front wheel) or get a Rigida Andra 30 Tungsten Carbide with the Rohloff drilling patten. The Ridgida are much cheaper and probably more robust but the Mavics are lighter, I can use the existing spokes and I like the 717's. My front wheel (717 not 517) is in great condition and has seen a similar mileage to the rear.
Incidental I wasn't riding my bike at the time the rim went - I was carrying it when I slip. The rim saw a large lateral force and a spoke popped
In these last last few months I seam to have has an unreasonable number of problems with my RST - I broken my saddle, a set of Avid Ultimate callipers - :'(, and now a rear wheel. The frame is as good as ever and so is the Rohloff so it's not all doom and gloom.
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Now do I go and buy a 717XC ceramic (to match my front wheel) or get a Rigida Andra 30 Tungsten Carbide with the Rohloff drilling patten.
I'm about to take my back wheel to a wheel builder to get it rebuilt after a spoke blew on me yesterday snapped about an inch away from the nipple). Never happened to me before, but I've never been this heavy before, I guess. I bought the wheel (because it had a Rohloff hub) on Ebay, so I don't know its history and I've lost a bit of confidence in it now, so I'll get all the spokes replaced, and maybe even consider a new rim while I'm at it. The chap I spoke to mentioned that he had Mavic 717 and 719 in stock, but this thread has put me off a bit!
Can I ask - what is the 'Rohloff drilling pattern'? I've been slightly suspicious of the way my existing spokes exit the nipples - they exit at a fairly sharp angle to the line of the nipple, but I've always shrugged that off as an inevitable feature on a wheel with a large-diameter hub. Is there some advice I should pass on to the wheel builder, in case he's not familiar with Rohloffs?
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Hi Stutho, what happened to the avid ultimates? I got one replaced under warranty because a tiny metal boss that the fine adjusting screw pushes against broke off on one caliper. This disabled the brake as I couldn't keep it off the rim. I went ahead and bought another straightaway (hence the replacement being oferred below in the small ads).
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A Rohloff drilling pattern has slightly 'cambered' holes so that the spokes point more directly at the flange and don't need to bend as sharply as they exit the rim.
I don't think my CR18s have them and I never broke a spoke (actually never in my life).
I think the Rigida Andra Carbide will be my next rim.
I'm not too sure about the front but I reckon they will make my rear wheel into a 'fit and forget' item.
My Rear CR18 lasted just under 8000 miles before the sidewall caved in and cracked. I tend to drag the rear brake on long steep descents which won't help but the main problem is riding on gritty country lanes in all weathers. It's quite hilly round here so you tend to be climbing slowly or descending quickly. Brakes/rims take a beating.
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Geocycle,
That sounds like exactly the fault that I had. I have to admit that it was totally my own fault I was temperately switching the callipers over to a suspension forks. I was in a hurry and I tightened down that little metal prong onto the adjustment screw snapping the prong I was not a happy person for the rest of the day - I hate braking kit through stupidity.
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Sounds like a bit of a weakness on what is otherwise an excellent product.
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Al Downie,
The chap I spoke to mentioned that he had Mavic 717 and 719 in stock, but this thread has put me off a bit!
I am still a fan on the 717 Note the wheel I just damaged was a 517. I have built up 5 wheels with 717 rims - All are still true even after some abuse. The thing with rims is that there are different horses for different courses. If you intend to use the bike for heavy off-road touring then maybe this is not the rim for you. If like me you spend 98% of your time on tarmac then the 717 it is a good bet.
Re Rohloff drilling pattern, its a freddered said.
If you build up a 717 with a Speedhub then the spokes wont line up properly with the eyelets. HOWEVER if you are careful during the build you can slightly cold set the eyelets with a metal rod. (Credit to Andy at SJSC) PLEASE proceed with caution and don't blame me (or Andy) it goes wrong. There are many times more wheels out there with speedhubs that don't have the correct drilling patten than those that do so don't be too concerned about it.
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Howdy all,
Bit miffed to see the original post about the 717 cracking. I for one rejoiced and celebrated when that rim was released. It's vastly different from the old 517 in that it has what Mavic call "H2 Technology": Hammer Hardening. This is where they 'hammer' the the heck out of the rim around the spoke holes before installing the eyelets to make the metal stronger and less prone to cracking.
Why did I rejoice? Well, a highly strung wheel (i.e. with the spokes at higher tensions) is a stronger and longer lastly wheel. The 517s couldn't be built that tight without cracks appearing in not too much time.
And as for the 717s? I love building wheels with those rims. I've got several myself and you can take the spoke tension to a lovely and tight 1100N and they roll true and straight with no broken spokes forever and ever and ever.
EX721: These are my rims of choice for touring as you can put wider tyres on them than on 717s. I've used loads over the years and they've all died from being worn out (the braking surfaces aren't that keen on the constant stop-start of commuting in all weathers). I now use a disc brake on the back of my Raven Nomad. I've used Sapim Race double butted spokes and have 'abused' the wheel quite a lot with no cracks, broken spokes or out-of-trueness. As for tyre pressure, I've a Schwalbe Marathon 2.0 on the rear and have run it at 80psi for over a year with no problems.
A note on spokes: in my youth I was instructed that plain guage spokes were stronger so when I first built up a Rohloff hub to go on my mountain bike I used Sapim Leader, non-butted spokes. I had two spokes break inside a year. Then I learnt the truth about spokes: wheels built with double-butted spokes are stronger and last longer. When the rim wore out I rebuilt it with double-butted spokes and it's been beautifully wonderful since. 'Course, now I've said that I'll probably start snapping spokes all over the place. I've recycled the 721 that wore out onto a disc brake wheel and have given it some punishment. It doesn't seem phased that it was previously built on a Rohloff and so had the spokes arriving at it at a very different angle.
A note on messing around with the eyelets on your 717s: stuff that! No offence to Andy and to wheels that have had it done and survived, but those rims are precision made and I wouldn't want to mess around with what those clever Frenchies have done. Wheel building's all about using decent spokes and nipples and getting the correct tension (i.e. as high as the weakest link can take). I've found that Sapim's brass nipples have enough of a rounded profile around the head for large flange Rohloffs not to be a problem.
Congratulations of you're still reading and I hope some of this is of help to someone. :-)