GP4000s measure 27mm on 14mm internal / 19mm external width

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bm0p700f
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by bm0p700f

Every rim I have tried the conti GP4000s on and this goes for other tyres too they are narrower on narrow rims compared to wider ones without exception.

I for one find the way the bike handles on 23mm GP4000s on mavic CXP14 rims to be completely different and less favourable to a similar depth wider rim where the tyre sits wider. On rough roads I simply get thrown around more and bends can be rough as well. tyres on wide rims dont square off as quickly either that helps.

23mm GP4000s on 15mm intenal width rims are 23mm for me. on an H plus Son archetype they 25mm. On an HED Belgium+ they are 26mm on my 25mm carbon rims they are 26mm
25mm GP4000s on HED rims are 28mm!

Gatorskin 23mm on mavic rims are 23mm but on wide rims they are 25mm
the 28mm tyre on mavic rims are 26mm but on a wide rim they ae 28mm

27mm Vittoria Open Pave on a Kinlin XR200 is 25mm wide. On a wide rim (archetype) it is 27mm.

Need I go on. I have tried alot of tyres and alot of rims and all but a few (22mm veloflex corsa's for example) did not spread on a wider rim.

So I cannot understand the posts above. It sounds like the GP4000s is a bit variable in width but one effect I have noticed is that tyres take on different width on rims with the same internal diameter. The bead hook seems to make a difference don't know why though. It not the extra width though that helps it is the change in tyre shape. All these things though are maginal gains, this one is worth having though especially if you have to change your wheels. On smooth roads I would agree the handling improvements are not big it rougher roads (all the roads I ride on are like this) are where it starts to help.

On handling. Tubular tyres tend to offer better grip. Part of the reason is tyre shape (it not huge improvement but it is there) and clinchers on wide rims have a similar tyre shape so there is the reasoning.

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Marin
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by Marin

I think that wider tires handle a bit better in general, but I doesn't matter where the width comes from?

rpenmanparker
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by rpenmanparker

Current wisdom is the flatter profile of the narrow tire on a wider rim gives better handling than the "light bulb" shape you get with a wider tire on a narrower rim. Less "squishy".
Robert

Fiery
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by Fiery

Marin wrote:I'm running rims from 13 to 18.5mm internal width and I can't detect any difference in handling. I'm a pretty good descender - ex-BMX racer and rode a lot of MTB too.

However, rim width did make a difference for MTB tires.
Going from 19mm to 25mm internal rims with 60mm (2.4") tires at 1.5-1.8 bars makes the sidewalls less likely to fold over during hard cornering - but there we had tires at 3x the rim witdh, at super low pressures. The fix for narrow rims was to run 2 bars instead...

A 23mm tire is not even 1.5 times wider than a narrow road rim, and will be run at 7-9 bars, so handling won't be affected. If anything, I suspect that "vertical" sidewalls (narrow tire on wide rim) don't work that well.

Summary: Don't believe the hype.

Have you tried to lower the pressure when going to a wider rim? My understanding is that the wider rim enables you to lower the pressure for a more comfortable ride without adversely affecting the handling. I haven't had a chance to try this, so I'm asking those who have.

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mpulsiv
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by mpulsiv

http://flocycling.blogspot.com/2011/11/flo-cyling-contact-patch-why-wider-is.html
http://flocycling.blogspot.com/2011/08/flo-cycling-component-series-part-4-flo.html

These blogs got me sold on wide rims. I was hoping to gain extra width and a bit more comfort (especially when racing on chipseal) with lower tire pressure. My narrow rims are more than adequate, 27mm wide running 85 ~ 90 psi, no pinch flats on GP4000s. Aero is least of my worries. I guess I won't be upgrading to Pacenti SL23 or FLO 30 after all.
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AJS914
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by AJS914

It seems like the differences are small, not enough at least to replace a perfectly good set of "narrow" rims. But if you needed a new set of wheels then go wider by all means.

Marin
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by Marin

Fiery wrote:Have you tried to lower the pressure when going to a wider rim? My understanding is that the wider rim enables you to lower the pressure for a more comfortable ride without adversely affecting the handling. I haven't had a chance to try this, so I'm asking those who have.



Wider tires are harder at a given pressure, so you run them at lower pressure to have the same level of comfort anyway.

rpenmanparker
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by rpenmanparker

Marin wrote:
Fiery wrote:Have you tried to lower the pressure when going to a wider rim? My understanding is that the wider rim enables you to lower the pressure for a more comfortable ride without adversely affecting the handling. I haven't had a chance to try this, so I'm asking those who have.



Wider tires are harder at a given pressure, so you run them at lower pressure to have the same level of comfort anyway.

And wider rims result in wider tires when using a narrower tire, so lower pressure is expected in a tire when moving up to a wider rim.
Robert

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