27" converted to 700c - how to fit mudguards?

[DCBassman]

For the Revell mixte.
Haven't bought any yet, but while I can see that stays should be ok to fiddle with, the chainstay bridge and brake bridge will be a bit distant.
Or should I fit much bigger tyres and fit 27" guards?
I can put up to 32s on the rims currently fitted.

 

[goldcoastjon]

I would fit 32mm tires in any case if they fit, for better flat resistance, load carrying, and better resistance to flattened and dented rims... ;-)

Doing this will also help reduce the fender-to-tire clearance, of course.

 

[a.twiddler]

I would fit 32mm tires in any case if they fit, for better flat resistance, load carrying, and better resistance to flattened and dented rims... ;-)

Doing this will also help reduce the fender-to-tire clearance, of course.

How about this? Problem Solvers Fender Flute from SJS cycles. At £17.99 maybe a bit pricey but perhaps you could make something similar. It solves the mudguard gap problem.

 

[tyred]

If you use 32mm tyres it will only be about 4mm difference in wheel radius which will barely be noticed.

 

[goldcoastjon]

How about this? Problem Solvers Fender Flute from SJS cycles. At £17.99 maybe a bit pricey but perhaps you could make something similar. It solves the mudguard gap problem. View attachment 635405

View attachment 635406

What a cool widget! Why WILL they think of next? ;-)

 

[si_c]

If you use 32mm tyres it will only be about 4mm difference in wheel radius which will barely be noticed.

This pretty much, the diameter of a 27x1.25" tyre is about the same as a 700x35c tyre, so anything less than that will probably be a reasonable fit. I did a 700c conversion with an older bike and it was fine. I used an angled bracket to make an adapter for the rear mudguard which worked well, and a standard mudguard on the front fitted fine.

You should be able to adjust the guards with a little bit of lateral thinking with little difficulty. 27" mudguards with a 700c wheels will work more or less but here will be a bit of a noticeable gap between the tyre and guard so might not be as effective as a close fitting one.

 

[Ajax Bay]

700c = 622mm diameter; 27" = 630mm.
Radius difference is 4mm.
The fork is likely designed to accommodate a 27" x 11/2" tyres so a radius of 334mm.
A 622 with a 32 on has a (rough) radius of 327.
7mm is a fair gap for an effective mudguard (hence OP's post).
My first stab (not based on experience) would be a simple extension steel strap from the (assume caliper) mounting hole in the fork down to the normal fitting on the mudguard. To get the rigidity better (acceptable will be a judgement for the OP but trialling this would be cheap), double bolt at the mudguard fitting end. The SKS one I have ready to fit has a 16mmx6mm slot in the fitting: enough for two M5 bolts.

 

[tyred]

I would suggest that the effectiveness or otherwise of a mudguard is more likely to relate to it's width in relation to the tyre. It needs to be wider than the tyre to work effectively. It also needs to be a decent length and ideally have a mud flap fitted.

Look at a vintage roadster - wide guards with a gap and very effective. A mudguard very close to the tyre just gets stones, leaves and other rubbish stuck in it.