Mudguard Rubbage

[rob]

Morning

The Dolan has 'guards and 25c tyres which are at the recommended limit.   In the garage and standing still the wheels spin smoothly and the everything seems adjusted correctly, but the guards need clearing out after any skoggy excursions.

However, the rear mudguard rubs when I'm sat on the bike.   It rubs more when I'm sat on the saddle and less when standing on the pedals.  So far I've largely put up with it as a little annoying but it seemed to get worse on my ride last night to the point where I stopped and took the wheel out to see if there was an obvious cause.   It also stops when braking.

I've not gone and had a look today, but I'm suspecting something around the bracket at the brake bridge.   Anyone else had similar ?

[Ben T]

Bike marketing literature can be a little liberal in terms of the description of clearance abilities:
i.e. "takes 25mm tyres/mudguards!"
doesn't mean "takes 25mm tyres WITH mudguards"
it actually means "takes 25mm tyres OR mudguards"
 

[LittleWheelsandBig]

Where is the tightest clearance?

Is it intermittent (every or every second pedal stroke) or continuous rubbing?

Is there a crack in the mudguard itself or mudguard bracket or frame?

Are there rub marks on the tyre or rim?

[Dave_C]

Does it rub in one place on the tyre? By this I mean one spot? The tyre could maybe require reseating? It is an easy thing to do.

If not and it is rubbing in one line around the tyre, try someone's rollers and ask them if they can scrutinise the rear wheel to see if they can see or hear where it is rubbing.

I have two Dolan Dual's, and the bike with the original and guards are snug when I have conti gp4000 tyres on. The same when I put Schwab marathon 25 tyres on. Which tyres are you using?

Would the frame be flexing with your weight on it? Is your Dolan carbon or aluminium?

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[robgul]

As suggested check tyres for "roundness" and seating on the rim - I had a pair of Schwalbe Pro One tyres (bought as a package) that had a bulge and caused a once per revolution rub on the rear brake bridge* - I had checked the seating of the bead several times ... even moving the tyre name out of alignment with the valve stem! - no improvement and the supplier (can't remember who) exchanged the tyres - replacement pair were no problem.   Putting the rear wheel in the truing jig showed the bulge was getting on for 4mm (very tight fit on a PlanetX Evo Carbon frame)

* a friend rode behind me and spotted what was going on

Rob

[rob]

It was originally intermittent on the pedal stroke which I put down to the frame flexing.   It's carbon and I don't put out a massive amount of power.   

The more recent rub is consistent and is there when I'm freewheeling.   The clearance is very tight between guard and tyre between the BB and the brake bridge.   I'm running 25c Conti GP 4 Seasons on Pacenti Forzas.

I'll pop the wheel out later and have a good look.

[Cudzoziemiec]

You say it rubs when you're sitting on the bike, but what if you're sitting but not riding? Maybe on a turbo where there are no bumpy roads?

[Dave_C]

...  I'm running 25c Conti GP 4 Seasons on Pacenti Forzas.

I'll pop the wheel out later and have a good look.

Could the rim have an effect. My Dual runs on Ambrosio Excellence rims and I have no rub, and infact plenty of clearance as I have put the mudguards on as far out from the tyres as possible.

Do you have any other wheels you can put on the rear to check?

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[Brucey]

IME it is most likely that the wheel is moving around under load, either in the hub (eg bearings) or in the wheel itself (spokes slightly loose, that kind of thing).

If there is contact there will be a mark; you just have not found it yet. A second pair of eyes can be a great help.

BTW if the tyres are newish they can have 'moulding sprues' on the sides and these tiny pieces of rubber can rub, make noises etc in a surprising way.

cheers

[mrcharly-YHT]

GP 4 seasons measure up small.

I agree with brucey. A tiny bit of play in the bearings can result in a large rim movement. So can a broken axle.

[rob]

GP 4 seasons measure up small.

I agree with brucey. A tiny bit of play in the bearings can result in a large rim movement. So can a broken axle.

I hope not.   Brand new DT Swiss hubs with around a 1000 miles on them.   I'll have a look.

[zigzag]

ideally the gap between the tyre and mudguard should be in a range of 1-1.5cm, equidistant all around. if it's less, there might be rubbing, going over potholes, sprinting out of saddle, skog being collected and rubbing. i would check if it is possible to move the mudguard away from the tyre.

[rob]

There is no play in the hub and the wheel is true.   There's maybe a mm of height difference in the tyre as it spins.

The rubbage seems to be around the brake bridge.   It looks like it hasn't been nipped up tight enough or flush to the guard so there's maybe room to do something there.   I could also remove the bridge completely, drill the guard and use a cable tie round the brake bolt, which would give 3-4mm of extra room there and help to position the guard between there and the BB a bit further away from the tyre.

The job might have to wait a week or so, though.

[Brucey]

if your mudguard bridge is fitted like this



i.e. immediately below the seatstay brace, then it is robbing you of precious clearance.   It should be fitted to one side if you want it to fit with best clearance.  However if you have a (stupid) modern  frame that uses allen key fittings for the brakes (even though it is meant to take mudguards and doesn't have clearance to spare) then you can't easily fit the mudguard bridge where it ought to be.

You can use zip ties (bleuch) if you want but you can also

- use 'Sheldon fender nuts' or
- fit a proper centrebolt to the rear brake

instead.

cheers

[rob]

I’m afraid the mudguard bridge is below the brake bridge and the brakes are hex key fitting.

I’ll look at the other suggested solutions but I have previously got round this by removing the brake bridge fitting, drilling 2 small holes and running a cable tie round the brake bolt.   It’s not need but it gives you a load more clearance and is reasonably secure.

Thanks

Rob

[rob]

Sheldon Fender Nuts look like an elegant solution.   Ta.

[Frank9755]

I’ll look at the other suggested solutions but I have previously got round this by removing the brake bridge fitting, drilling 2 small holes and running a cable tie round the brake bolt.   It’s not need but it gives you a load more clearance and is reasonably secure.

I did that on a bike recently to solve a similar issue.  I probaby have it on the majority of my bikes.  I don't know why they don't just not bother with the bridge fitting and pre-drill two little holes as the challenge is always getting them equidistant from the centre-line...

[aidan.f]

Two pairs of holes on outside edge of guard then ties over the bridge arms is even better for max clearance. Can look quite neat imo.

[Dave_C]

Two pairs of holes on outside edge of guard then ties over the bridge arms is even better for max clearance. Can look quite neat imo.

This is what you have on the rear wheels of your trike right?

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[aidan.f]

Err no..just air

[Dave_C]

Err no..just air

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[GrahamG]

Do have a good look over the frame to rule it out, I've just had to bin a set of forks after a similar annoying mudguard rub started - bonded alu crown had starting corroding and I hadn't noticed the bubbling paint,  I'm assuming it led to a slight warping where the carbon blades were bonded in. Glad I'd pushed the clearance with a 28 in that instance! 

I think i have some sheldon/problem solver fender nuts in the spares box if you want them..

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[rob]

I think i have some sheldon/problem solver fender nuts in the spares box if you want them.

Thanks for the offer but I’m afraid I bought some from SJS a bit earlier.


Rob

[rob]

Fender nuts have spaced out the guard nicely and I managed to remove the bridge, flip it round and pinch it back up nicely.

Annoyingly the tyre is now rubbing on the bolt that attaches the guard to the chain stay bridge just behind the BB.  There’s a washer just under it that I could remove but I’ve now rounded the hex bolt.  Off to the shop it is then.

[giropaul]

Tyres vary a lot in the height from the rim. Continentals are quite high. Vittoria Open CX and Veloflex give much more clearance.