Author Topic: Clearance and appearance  (Read 1268 times)

tyreon

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Clearance and appearance
« on: August 18, 2021, 08:39:56 AM »
Cycling x2 20 x 1.5 Schwalbe Marathons. I would like a Schwalbe Marathon Plus 20x 1.5 on the rear for additional security. Unfortunately Shwalbe dont do 'em. So 20 x 1.35 or 20 x 1.75? I am worried about 1.75 clearance with my mudguards,but wouldnt like to undo the uniformity of the appearance of the tyre(s) on the bike by having the rear tyre looking at odds with the wider tread of the tyre being on the front. Still...

Go less, or more?

Appearance wise,is their much difference between a 1.5 and 1.35. If the 1.35 was at the front I dont feel it would compromise the appearance of the bike. But t'other way round?

1.75 might just catch those guards......maybe...?

Your thoughts?

JohnR

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Re: Clearance and appearance
« Reply #1 on: August 18, 2021, 10:04:38 AM »
I can more easily visualise small numbers in millimetres: 1.5 inches is 38.1mm. 1.35 inches is 34.3mm (- 3.8mm) and 1.75 inches is 44.4mm (+6.3mm). 3.8mm isn't much of a difference and I suspect will be barely noticeable, particularly since half the tyre is covered by the mudguard. Nonetheless, there's logic in having the rear tyre larger since it's carrying more load. Is there any potential for moving the rear mudguard out slightly if necessary? There's also the issue of nominal vs actual tyre sizes with the latter also being affected by the rims (see https://www.bicyclerollingresistance.com/specials/schwalbe-marathon-32-37-40-47 for some examples of actual measurements). You'll only find out how the actual tyre sizes compare by fitting them to your rims. Or would an alternative strategy to improve puncture tolerance be to put some sealant in the inner tubes?

PH

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Re: Clearance and appearance
« Reply #2 on: August 18, 2021, 12:16:52 PM »
Clearance - Suck it and see.  Get some cloth, or paper and some tape of some sort and wrap it around a small section of the current tyre till it measures 1.75.  Spin it and see how it clears the guard.  Ideally you'll have 10mm of clearance on all sides, this seems to be the happy medium between best coverage and not getting clogged up.  If the guards have been neatly fitted around the current tyre size, there may not be any spare in the stays to let them out, but replacement stays are available.
Appearance - I run a wider tyre at the back on several bikes as a preference, 32/28, 40/35, 2"/2.15".  If anyone has noticed, they haven't commented and I frequently ride with the sorts of people who like to comment ;)
I think you'd have to be looking closely to notice the difference between 1.5 and 1.75, IMO you're more likely to notice the extra comfort, though that my be negated by the "Plus"

lewis noble

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Re: Clearance and appearance
« Reply #3 on: August 18, 2021, 12:44:15 PM »
I think a lot also depends on the sort of terrain you ride in.

My Mk 3 Audax was originally specced with 700/32 Supremes - and yes, as the brochure states, they did fit - just - with obviously extremely careful mudguard installation by Thorn.  They gave a lovely ride.

But at the time, a lot of the roads in our city (Sheffield) were being resurfaced / rebuilt . . . . . and gravel on the road surfaces was very common.  Gravel pieces stuck and scraped between the tyre and guard; never actually jammed or even perceptibly slowed me down, but I found it unnerving and not a good thing. 

The same happened on some of the rural roads around here.

So I swapped to 700/28s. Ride not quite as good, but less scraping and chattering.  If I could me more confident about surface quality on a long tour, I would probably revert to 32s.

I'm keen on quite generous clearance.

Lewis
 

tyreon

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Re: Clearance and appearance
« Reply #4 on: August 19, 2021, 08:37:24 AM »
I would like to thank all those who replied to my query: thanks.

 I will do another sighting review of the clearances I have.

Its an irksome problem

I am not one for close tolerences. And too close can bring chatter or noise...and aint right!

tyreon

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Re: Clearance and appearance
« Reply #5 on: August 22, 2021, 09:07:55 AM »
Update: Ordered 1.35 shwalbe marathon plus. 1.5 started rubbing rear mudguard yesterday after getting bike out from the car. Irksome

Andre Jute

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Re: Clearance and appearance
« Reply #6 on: September 17, 2021, 03:15:50 PM »
0.15in is 3.8mm. Whether it will be enough extra clearance will depend on where you ride, as Lewis says. I've ridden for years with tiny clearances, between one and five millimeters, but I ride almost exclusively on clean blacktop, though the surface is potholed. I've found that the potholes are not a problem for clearance (though twice in a dozen years fishmouth punctures have caused spectacular decompressions in my ultra-low inflation regime, one of which caused a serious accident that could easily have been fatal were it not for the quick reactions of the motorists behind me) but cheap chip and seal roadworks cause nasty chattering and scraping between the tyre and the mudguard. To avoid giving up my beloved Big Apples or even scale them down*, I just don't ride on newly remade roads -- there's always a parallel lane.

*The late Kalle Kalkhoff, who developed the best of the modern Pedersens (now manufactured by Utopia-Velo in Germany, who bought the manufacturing rights), told me that he envied the 60mm Big Apples on my utility bike, but he'd have to sacrifice the mudguards on his bike, so he rode in the winter on 50mm Big Apples. In the summer he threw the mudguards off and felt no envy on 60mm Big Apples. He pointed out that a 50mm balloon already contains 50% more air than a 38mm tyre. Later I worked out why the effort was worth it for him: a 60mm tyre contains 50% more air again than a 50mm tyre. Regardless of your attitude to restrictive clearances, for comfort and roadholding your tyres should be the biggest you can usefully fit on your roads.