Cant figure out what is wrong with my Titus Supermoto……..

I changed over the brakes from Shimano XT’s to some big ol’ avids and thought is was the pads rubbing on the rotor so sorted that out.

I had also changed from the small diameter cassette to what I think is a SRAM PG970 MTB Downhill Cassette as seen here

http://www.chainreactioncycles.com/Models.aspx?ModelID=57562

Well, it is the same colour scheme and I havent seen another llike it so assume it is that one.

Anyway, when I now tighten up the QR, the wheel spins fine in reverse but when peddling on the bike rack, it is bloody stiff. I have loosen the QR off until it is almost falling out of teh frame before it moves freely when peddling.

Any ideas from the Forum Pro’s?

Is it the cassette? I thought you could use SRAM cassettes with Shimano chains?

Is teh cassette too fat? Cant see why this would make a difference as it was a 9speed on there before but just much smaller in diameter.

Any suggestions galdly welcomed.

kind regards

Ben

I am going to take a guess at the new cassette has now made the chain to short making the drivetrain tight. As i said it is a guess, but it is easy to check. Put the bike into a middle gear front and back and see if you still have the problem then try and shift up into the bigger rings, if your problem comes back the chain is too short.

if it spins freely backwards but won’t pedal forwards properly then i’d tend to think that either the rear mech is catching the cassette as you pedal (if you fitted a larger diameter cassette but didn’t increase the chain length then the mech will be pulled up towards the cassette) or the chain tension is now too tight and makes motion difficult, does it stay the same through all gears ? or is it just the larger cogs.
edit: too slow!.

What hub are you using? I assume it was fine before changing the cassette?

Hard to say without more info, your best bet is to evaluate exactly what is happening and determine where the problem is by observation. rotate as many individual parts independently and see if any of them is the cause.

For example jockey wheels, free hub, everything that could cause this effect should be checked, including the hubs function.

Good luck.

Thanks Chaps

The chain was brand new, out the box and was shimano 9speed – it isnt tight at all adn the problem occurs through all ranges of gears.

The top of the mech looks close to the cassette but not overly and is not touching.

The hubs are fine, minimal use and are Bonty Big Earls so pretty decent pieces.

Dammed pesky as this fat lardy &rse really wanted to begin cycling again and was to start into work to get some cardio before going snowboarding in three weeks time.

Ben

I just swapped to a spare back wheel on my road bike and was having a similar problem. For me it turned out that there was a slight difference in the hub spacing meaning that the teeth of the smallest cog were just scraping on the frame. I popped a washer on the axle and it cured the problem. (I only needed a temporary fix until I get my good wheel back on).

You mention that you have changed your cassette – might it be catching on the frame for you?

I did look at the inner cog and it doesnt seem to be catching anywhere but may be an option to try.

Thank you for that.

Ben

ok do you have cup and cone bearings or cartridge type in your hub? i only ask as you say it’s only when you undo the qr that it pedals freely, if you tighten the qr and that makes it stiffen up then your cones might be a tad too tight when the qr is done up, try adjusting the cones a little to loosen it off.

All – would it be a problem if the cassette is a narrow gauge cassette and the chain is a standard Deor chain?

Is a specialised chain required for a narrow DH style cassette?

Thanks

Ben

no such thing as a narrow cassette – if it has x gears then its the same width

is the casette full back on the freehub?

Hi 5lab, yes, I am sure it is as it was well tightened up.

Please do excuse my ignorance as I am not fully clued up with Bike Mechanics but am desperately trying to learn.

The wheel spins perfectly in reverse but it is only when spinning the cranks (on the bike stand) that it is stiff.

Unfortunately, I am half deaf but am sure I can hear some sort of humming/whirring/grinding coming from the rear when I do this. Natrually, I am not keen to continue this form of testing 😕

Sorry, I thought that there were narrow cassettes as they use in road biking or is this a misnomer on my part?

This is what the cassette looks like (http://www.jejamescycles.co.uk/sram-pg970-9-item148624.html) but have read that, being a 9 speed, any 9 speed chain will suit and I have a brand new Shimano 9 speed on the bike.

Any thoughts as I am sure you all know much more than I do 😳

Remove brake caliper to eliminate that.
Refit old cassete to eliminate that
Could it be a seized/tightening bottom bracket?
Has bike been laid up for a bit?

Lift the chain off the chainset and try turning the crank – is it stiff? That will rule out the bottom bracket.

Does the wheel turn freely both ways when a chain isn’t fitted to the cassette?

Broken axle? I had this with a Hope hub x 2 🙄

it sounds like the rear end of the bike is clamping on the casette, rather than on the bearings of the rear axle. My guess would be that if you take the chain off completely, the wheel will go forwards smoothly, but backwards slowly with friction (??)

did you fit the casette with the lockring which came with the casette? (if, say, you only had a shimano lockring tool??) if its possible you used the old one, I guess it might not fit the new cassette, which could mean its sticking out further, interfereing with the dropouts? the dropouts should clamp on the axel, and not touch the casette\lock ring at all

5lab

I used the locking ring that came with this dastardly cassette.

I will change back to the other after checking your suggestion re the dropout interference.

Thank you to all the ‘Pro-Panel’!

regards

Ben