Stones getting jammed between rear tyre and brake caliper

[Boogaloo]

I bought a Canyon Endurace last autumn with Ultegra rim brakes. It came with Conti GP4000S II in 25mm and on a regular basis I am experiencing stones getting picked up by the tyre and jammed between the tyre and the caliper (rear wheel).

As the cross section profile of the calipers is effectively wedge shaped any stone of the right (wrong) size entering this space is bound to get stuck and I am required to stop and spin the wheel backwards to clear it, With the road dressing season in full swing this is happening on multiple occasions per ride and is pretty alarming each and every time.

Is anyone else experiencing this?

My previous bike - a Bianchi with Daytona calipers and tyres from 19 - 25 mm never did this during the tens of thousands of miles we rode.

I did fabricate a sort of stone deflector that fitted to the caliper mount and passed between the tyre and caliper. This worked well but limited me to 25mm tyres and I have just changed to 28mm (Still GP4000S) and had to remove it as there isn't enough space. The stone jamming has returned.

Obviously I could go back to 25mm and replace the deflector but I feel that I shouldn't have to be doing this.

Anyone got any ideas?

Thanks

Paul

[tim-b]

Hi
Unfortunately a smaller tyre seems to be the answer; I get tar-sticky stones catching between my fork crown and tyre with 25mm tyres, scratching the underside, a 23mm front tyre has cured the problem
I also find that Contis (my tyre of choice) are sometimes a little larger than the nominal size suggests
Regards
tim-b

[Brucey]

fatter tyres and/or tyre savers



mounted so that the working part is the other side of the brake.

Also, don't fret, they will stop doing this sort of thing soon and anyway the stones won't stick because the roads will be wet...

cheers

[Grandad]

Can you still get that tyresaver? I used it when racing on tubs 50 years ago but thought it is now a museum piece, at least judging by what I got on e-bay when selling a pair a few years ago

[Grandad]

There was also a version that could be fitted to the mudguard.

[Brucey]

https://www.compasscycle.com/shop/components/fenders/tire-wipers/

Bit of a niche product these days....

but it is very easy to make your own. Some bits of old spoke and the kind of soft flexible tube that is used in aquariums usually does the trick.

cheers

[The utility cyclist]

That's the problem with some modern racing frame designs, simply rubbish clearance when there's absolutely no need to compromise in that area, it's not like the requirement for even an all out racing bike to have a bit more clearance for a wider tyre is unknown (and indeed the misunderstanding on aero which a narrower gap makes for worse airflow than a bigger gap) and for an endurance/sportive type frame it's ridiculous.
I have an ex works UCI conti pro team frame from 2013/14 and I can get 27mm tubs in and never had issues with stones using Dura Ace 9000 short drop.

[rjb]

And the cheap fix for those of more modest means was a strip of handlebar tape stuck across the back of the forks and stays which quickly wore down to the tyre profile.

No good if you had mudguards of course.

[Cugel]

That's the problem with some modern racing frame designs, simply rubbish clearance when there's absolutely no need to compromise in that area, it's not like the requirement for even an all out racing bike to have a bit more clearance for a wider tyre is unknown (and indeed the misunderstanding on aero which a narrower gap makes for worse airflow than a bigger gap) and for an endurance/sportive type frame it's ridiculous.
I have an ex works UCI conti pro team frame from 2013/14 and I can get 27mm tubs in and never had issues with stones using Dura Ace 9000 short drop.

The clearance gap between the brake/frame and the tyre isn't the issue. The issue is the shape of the gap between the brake/frame and the tyre.

I have a bike with a tiny clearance under the back brake for it's 28mm tyres. Nothing sticks in there unless it's sticky - i.e. recently tarred gravel on a newly-dressed road. Otherwise anything picked up either gets scraped off just in front of the gap or goes through.

The problem that the OP has seems to be caused, as he notes, by the "wedge-shaped" gap caused by the design of the brake calliper and/or the way it mounts to the brake bridge of the frame. The gap into which a stone can go is larger than the gap out of which some such stones can't go.

No matter if the gap is increased - it will simply allow larger stones to go into the gap and get caught because the exit-gap is a tidgy bit smaller than the stone size.

Cugel.

[foxyrider]

In sort of reverse order, I bought some flint catches for my Eroica build off Ebay - @£5 a pair.

As regards stone pickup - had it more than a few times running 23mm GP4000sII's (the frame won't take anything bigger anyhow) through Super Record calipers and the brakes have the marks to prove it! More worrying was when it did the same on the front whilst cornering - scary moment but it cleared through before it caused an issue more than brown pants! Maybe a return to old technology is the way forward.

Wouldn't mind if it actually improved the roads rather than just hiding the imperfections! Even worse, Derbyshire CC have a habit of laying beautiful smooth tarmac which they then 'dress' 6 months later - grrrrr!

[David9694]

Tyre savers as pictured: surely not going to solve the OP’s problem as the picked up stone reaches the area of the Caliper before the saver does its thing?

Not had the specific problem myself, but melty road surfaces in the heatwave have tended to mean more stones get picked up, but they don’t hang around IME.

[The utility cyclist]

That's the problem with some modern racing frame designs, simply rubbish clearance when there's absolutely no need to compromise in that area, it's not like the requirement for even an all out racing bike to have a bit more clearance for a wider tyre is unknown (and indeed the misunderstanding on aero which a narrower gap makes for worse airflow than a bigger gap) and for an endurance/sportive type frame it's ridiculous.
I have an ex works UCI conti pro team frame from 2013/14 and I can get 27mm tubs in and never had issues with stones using Dura Ace 9000 short drop.

The clearance gap between the brake/frame and the tyre isn't the issue. The issue is the shape of the gap between the brake/frame and the tyre.

I have a bike with a tiny clearance under the back brake for it's 28mm tyres. Nothing sticks in there unless it's sticky - i.e. recently tarred gravel on a newly-dressed road. Otherwise anything picked up either gets scraped off just in front of the gap or goes through.

The problem that the OP has seems to be caused, as he notes, by the "wedge-shaped" gap caused by the design of the brake calliper and/or the way it mounts to the brake bridge of the frame. The gap into which a stone can go is larger than the gap out of which some such stones can't go.

No matter if the gap is increased - it will simply allow larger stones to go into the gap and get caught because the exit-gap is a tidgy bit smaller than the stone size.

Cugel.

If the tyre height* (which is generally higher on wider tyres on the same rim) you can comfortably get under the arch is say 28mm (as per the new Dura Ace 9100 design) compared to one that can fit only a 24mm height tyre (roughly what the 25mm GP4000IIs is) then you're less likely to have chippings get stuck than one that has a smaller clearance, the shape of the gap becomes redundant in the argument because you've physically made the gap much bigger and the give in the tyre as any chipping comes around is less likely to get jammed (because there's more room for it than there was before.
To suggest you'll get bigger stones/chippings in there as you have said has no merit to it IMO, chippings are fairly uniform in max size for one thing, secondly a bigger chipping is very much more likely to not adhere to the tyre than a smaller chipping, so what you describe isn't really a thing to consider.
/A wider rim should also reduce the height of a tyre at the same inflation

[Brucey]

Tyre savers as pictured: surely not going to solve the OP’s problem as the picked up stone reaches the area of the Caliper before the saver does its thing? .

read the words too; as previously described, it needs to be mounted round the other way.

cheers

[foxyrider]

Tyre savers as pictured: surely not going to solve the OP’s problem as the picked up stone reaches the area of the Caliper before the saver does its thing? .

read the words too; as previously described, it needs to be mounted round the other way.

cheers

Always used to have mine mounted through the rear brake! Of course their main purpose is to remove flints so as shown works for that purpose.

[Vorpal]

Can you modify the sahpe fo the clearance?

Can you post pictures? Maybe members will have some other suggestions?