slick tyres on an MTB

[i2000n]

A friend recently bought a Diamond Back MTB from Go Outdoors at under £300 with Rockshox Dart forks, Shimano gear and hydraulic disc brakes, which seemed like a very good deal. She swapped the tyres for 26 x 1.5 slick tyres as she uses it for commuting. The first time she used the bike she said that it skidded when she used the brakes. The shop said that she should not be using slick tyres with hydraulic brakes.. This is the first time I have heard of this as my wife's road bike has 700x 28 tyres with hydraulic brakes and she has no problem. Has anyone any experience of this?

[Trigger]

She should perhaps be using more front brake and less rear, unless it was a front end skid?

[meic]

It is funny the things that people in bike shops say isnt it?

I wonder if he* actually had any reason for saying that or he just opened his mouth and it fell out?
If there is a reason why slicks and hydraulics dont mix, I would take quite some convincing about it.

I can see that if you are on a mud slide with slick tyres and you use the full force of your disc brakes, you may possibly fall off.


* Yes, I know, sexist assumption.

[snibgo]

Welcome to the forum.

The first time she used the bike she said that it skidded when she used the brakes.

And the problem with that is ...?

If I pull very hard on my rear brake, and I'm going fairly slowly, the rear wheel will lock and skid. This should happen. Unlike modern cars, bikes don't have anti-lock brakes, so we have to learn how hard to squeeze the lever.

Similarly, pulling too hard on the front tends to lock that wheel, but the bike tips rather than skidding.

(My brakes are cantilever, and I'd expect disc brakes to be even more effective.)

[Hypocacculus]

I agree, the man in the bike shop was probably speaking out of an unsuitable orifice.

Skids are about failure of the road/tyre interface, not the type of brakes per se.

Disc brakes are, I gather, more efficient than rim brakes. If she isn't used to them, perhaps she overcooked it? On my old brakes, it didn't really matter how much brake I grabbed, the only increase in performance worth measuring was the volume of squeal (great for warning pedestrians though!). My new ones were a revelation - and they aren't even disc brakes. Or there was loose material/water on the road surface? Or are the slicks are some horrible cheap and nasty solid compound? Incorrect tyre pressures?

[bensonboo]

Have to agree with everyone else really, I'd be more concerned if a hydraulic disc brake COULD NOT lock either wheel, wet or dry. It's just a case of your friend learning to moderate her braking effort.

[uphillbothways]

Slick tyres and hydraulic brakes are a bad mix obviously, which is why Formula 1 cars and MotoGP bikes have such poor braking performance .

Your friend is probably trying to stop with the rear brake. As she slows down, her weight tips the bike forwards, taking her weight off the rear wheel, so she skids. Rear brake for slowing, front brake for stopping.

It's also possible that she has too much air in the tyres, which massively reduces grip and can make a bike feel really sketchy. This is easily done if a lightweight rider pumps up their tyres to the pressure marked on the sidewall.

[Simon E]

It's also possible that she has too much air in the tyres, which massively reduces grip and can make a bike feel really sketchy. This is easily done if a lightweight rider pumps up their tyres to the pressure marked on the sidewall.

Which is the maximum pressure for that tyre.

Schwalbe give a range of pressures for their tyres based on an average rider weight of 75 kg (165 lb):
http://www.schwalbetires.com/tech_info/ ... n_pressure

Michelin's road tyre PDF file only specifies 700c and 650x23c sizes while the equivalent for MTB tyres is intended for knobblies ridden offroad.

I run my 26x1.5" City Jets at 50-55psi (3.5 bar). Any more is uncomfortably harsh while less is draggy and the bike loses precision in handling. I think max pressure is 80 psi.

Braking technique is something that requires practice, and some degree of recalibration if you alter the brakes or tyres.

[CyberKnight]

I ran city jets at 80 and found them perfectly ok, as for the braking LBS is talking rowlocks

[DevonDamo]

When I recently bought a Kona Dew Deluxe hybrid, I stuck a pair of big fat slicks on it. On my way home from my first commute, I was turning right in front of oncoming traffic and my back end span round so far it almost left me facing the other way.

Hydraulic discs are powerful beasts. When you first ride a bike with them, you may well get caught out whilst cornering . Since then, I've been a lot more respectful of them and now wouldn't change them for the world - smooth as silk.

[LANDSURFER74]

All of this sounds like a good reason not to bother with hydraulic brakes.
If the braking forces overcome the friction of the tyres whats the point.. oh, sorry... they look good ... thats all that matters is'nt it!
And their expensive .. so they must be good ............

Form over function rules .....DOH!!

Now wheres my £135 cycling glasses ?.. the ones that look exactly the same as the safety glasses sold at my local work wear shop for £1.99.

All the gear .. no idea!

[Steve Kish]

I use hydraulic (Hope X2), calipers (Shimano Ultegra with Campag Veloce levers) and V-brakes (Shimano Deore LX, same levers) and TBH, the hydras easily out-perform the the other two in wet and muddy conditions. However, in normal conditions, I don't find much diffo between them all.

[DevonDamo]

All the gear .. no idea!

You win the 'Grumpy old Git' prize for June: a tube of Anusol and a box set of 'Ever Decreasing Circles' (on Betamax.)

[LANDSURFER74]

AT LAST!!! ... I'VE WON SOMETHING.......

[The Mechanic]

When I recently bought a Kona Dew Deluxe hybrid, I stuck a pair of big fat slicks on it. On my way home from my first commute, I was turning right in front of oncoming traffic and my back end span round so far it almost left me facing the other way.

Hydraulic discs are powerful beasts. When you first ride a bike with them, you may well get caught out whilst cornering . Since then, I've been a lot more respectful of them and now wouldn't change them for the world - smooth as silk.

OK, I'll stick my neck out on this. You shouldn't be turning and braking at the same time. That is a recipie for an off. You should slow to the right speed before the turn and do not touch the brakes until you are travelling in a straight line again. Yhis does not apply to offroad riding where sliding wheels is such fun.