Problem with my bike's handling

BG2000

I don't know if it's me getting less confident as I get older :oops: , or that something is wrong with my mountain bike. It just doesn't feel 'safe' any more :shock: , and seems too twitchy so I'd like to hear other people's opinion.

It just feels big and daft and clumsy. I realise now that the frame is too big for me, mainly the 63cm effective top tube length. I'm 6 feet tall, with a 34" inseam. I should be riding a 17" frame. However, I know other XC riders who have 'long and low' bikes too. That's how all MTBs where 15 years ago when I started racing.

I've noticed how clumsy my MTB feels since buying a cross bike, which actually copes better with slippery, rough conditions than my MTB. In other words, I feel more confident riding my cross bike off road than my MTB !

The MTB is a 19" Trek 8500 (year 2001). I replaced the original 80mm travel RockShox with 100mm travel Marzocchi MX-Comp ETA forks. Apart from new Mavic wheels, everything is pretty much the same as when new. I don't remember any such issues when I bought this 8 years ago.

The problem is that it feels like it wants to 'jack-knife'. It's not easy to explain, but when cornering, or riding through deep mud or rutted ground the bike doesn't like holding its line. It's as if the front wheel want's to tuck itself into the ground, and the frame carry on forward. I upgraded to some 630mm hi-rise bars (FSA XC-190) which made be slightly more upright, and with a wider cockpit, which helped a tiny bit.

Another way of describing the problem is when I'm climbing. I always lose momentum because the front wheel suddenly get's jerked off to one side, thowing me right off balance. The same happens especially if I'm riding through a rut. I just feel like the bike is trying to tip me off to the side. It's just too unpredictable. If I ride my cross bike through gloopy mud, you can just let the front-end take its own path, and as long as you keep the power on the pedals, you never lose momentum. But my MTB will suddenly throw you off at an angle forcing you to put a foot down. It just has this tendancy to want to whip the front wheel round. If I try and 'fight it' by holding the bars tighter, it means I'm not relaxed enough to 'go with the flow' as I can do on my cross bike.

This was especially problematic during recent snow rides this winter. I basically couldn't go down anything snowy/icy when using the front brake as I'd end up falling on my side as the bike jack-knifed.It's the fact that it jack-knifes so suddenly. I just can't predict what it's going to do.

There is no damage to anything, and everything appears to be in perfect working order. I've inspected everything. Overall, the bike rides very smoothly and silently.

I've had suggestions before on this problem:

" Try new tyres" . Well, I'm now running Maxxi Hi-Rollers in 2.3" width and it made no difference at all.

"Try hi-rise bars". This helped very slightly, but that could be placibo.

"Change stem". I've swapped between 100mm and 120mm, flipping them around - no difference.

"Your forks have too much travel for the frame geometry". Well, I've riden them at 80mm using the ETA lock-down and it makes no difference.

"Increase air pressure in fork". This made no difference. I've tried zero pressure up to 70 psi and it's all the same.

"You're too low at the front". Well, if this is the case, how is it that my cross bike handles better then ?

I don't expect anyone to 'fix' this for me without riding the bike, but any ideas will be much appreciated.

I should add that I'm perfectly willing to change frame. And if a 'trail' bike frame like a Marin Rocky Ridge or Cove HandJob will give me a more confident ride, while still giving a good setup for XC Racing, please feel free to suggest.

supersonic

First off read out what size thread - you may be a 17 inch in some frames, but they vary so much model to model you could be a complete range of sizes! Never assume you are just the one size.

I think the problem here is that the bike simply doesn't suit you - most likely the geometry is too steep making the handling nervous and twitchy. If you have tried all those adjustments then I think you should test ride some of the frames you suggest.

nicklouse

also a longer fork on an old frame can leave it feeling like the steering want to "fall over"

Put the ETA on and reduce the travel and see how it feels (dont hit any bumps with the ETA on though)

It will give you an idea if it is the fork that has whacked the geo out.

devondarren

It sounds to me that your forks just aren't up to the job. I rode with these forks on my old bike and the wheel flexes terribly, and does not inspire confidence. A new fork maybe the answer.

BG2000

nicklouse wrote:

also a longer fork on an old frame can leave it feeling like the steering want to "fall over"

That's exactly how it feels ! Well described.

This is why I'm unsure what to do. So many people have told me that the problem is with my bars being too low, 'cause it's an XC bike with long Top Tube and 5 degree rise stem. But when it feels like it wants to 'fall over' the bars feel like they're too high. The front end just seems to high up, bouncing all over the place. On my cross bike, which is much lower at the front end, you feel more confident being lower down, as if you're plowing through ruts and slippy mud.

So I can't imagine how it could be better on a trail/AM bike where the bars are even higher. I'd feel like I'm pratically falling off the back of the seat.

I'm meeting up with some MTB buddies this weekend, and will have a go on one of their AM bikes which they claim will 'show me the way' !!

supersonic

Hmm, so maybe the problem is that it is too slack! Usually slack head angles stabilize the steering - it wants to carry going on in a straight line. But at slow speed, it can cause the flopping sensation nick described. Especially if you have less weight on the front.

Steep angles respond quicker to your input, and the bars are more likely to get knocked off line (less self centreing).

Modern AM bikes tend to have quite slack head angles, but fairly steep seat angles to place the weight further forward.

djcombes

I've got a 2000 Trek 8500LT, which was a slightly more "trail" version of the same thing, supplied with a 100mm fork, Z3 flylights (long travel, as was). I always thought the frame was 18 inches, but I could be mistaken. I'm 6 foot, same size legs as you. Mine feels fine. I think it may be the forks that are the problem.

Mine came with risers - 600mm. It's now got 660mm risers, but still has the original 100mm stem.

Dunno if that helps or not really.

BG2000

Thanks for everyone's replies - I'm getting somewhere...

Here's a pic. Don't worry about the slick tyres and pannier rack - they're just what I use when taking my son to nursery. I swap the wheels with my proper off-road ones for the weekend !

But I think it shows everything looks 'normal' so it's not obvious (to me) what the problem is.



It's interesting reading supersonic's thoughts...I agree, and again, your description of 'floppy steering' sounds very familiar. You're talking about bringing the weight forward, and I agree. If I try to keep my weight back on climbs, the front end just wanders all over the place, and the slightest bump throws me right off line, stopping me dead in my tracks. But someone in a bike shop told me the 'floppy' steering is because I've got too much weight over the front wheel - I think that was rubbish, and my cross bike's handling proves that.

I did a sort of 'test' last night. I held the bike still on the garage floor, with the bars straight. If I then rotated the bars left and right, they always wanted to turn, and when you straightened them back up, you can see it 'lifting' the frame to do this, and hence doesn't want to self centre. On my cross bike, the frame stays still, and doesn't rise up down when you turn the bars. This must explain how when I'm riding the bikes, the MTB's steering feel unpredictable, as my weight is affecting the steering too much, whereas my cross bikes steering feels the same regardless of my speed and whether I'm sat back or forward.

I think this is a question of good design and geometry. My Marin cross bike has been well designed for its forks, stem, wheels etc..so it's all in balance. My Trek 8500 doesn't feel balanced at all. It's definately a 19.5" as I still have the sticker on it.

My local bike shop has a 17.5" Cove Stiffee ('09) on sale in Matt Black. I'm quite tempted. It's bound to handle better than what I've got. I'll never need to replace it, and can always upgrade my forks to get even better handling. I don't need to ask whether this frame is any good or not, that's an obvious question isn't it ?!!!!

Steve_b77

A 17.5" cove will be much too small if you're 6'3"

I ride a Handjob in the same size and I'm 5'11", the bike has a 90mm stem and it is on the short side, I feel I could ride the next size up comfortably.

I think the problem may lie in the fact that you're trying to moderinse an old frame.

The new forks may well be the same travel in ATA mode, but the Axle to Crown lenght may be far greater than the forks that came off the bike resulting in a much slacker head angle.

supersonic

Looking at a pic of the bike it looks far from slack angled - quite steep!

So as before, i think you need to try some bikes out to see what suits you - some prefer the fast handling, some like a more relaxed feel.

BG2000

Cheers Steve,

Actually, I'm 5ft 11" and a bit....and my current Easton EA70 stem is 120mm length, so I think the 17.5" Stiffee will be ace.

I want a frame that's not as long (effective TT length), to do more technical rides.

The Stiffee has a 23" effective TT length, whereas my Trek is 25.5" !!!

You're right about the fork length issue, travel doesn't tell you everything w.r.t. height.

The headtube is shorter on the Stiffee, so I may even end up with a similar bar height, which is fine by me, if they're a couple of inches closer. I can always flip the stem.

BG2000

supersonic wrote:

Looking at a pic of the bike it looks far from slack angled - quite steep!

So as before, i think you need to try some bikes out to see what suits you - some prefer the fast handling, some like a more relaxed feel.

I had thought about doing test rides, but as I'm only changing the frame, it wouldn't guarantee it'll feel the same as a good test bike once I've built it up.

One reason I'm interested in the Stiffee is that it will always have the potential (with a good fork upgrade) to be as good as I'll get for a hardtail. I may need to change other parts (stem, bolt through front wheel etc..) but at least I'll stop thinking "perhaps I need a more stable frame" when I'll have the best there is, end of story. I'm not 100% sure yet, although that's mainly because it's a lot of money for a frame. And they only have matt black, which I'm not so sure about.

supersonic

But you may make things worse! There is no doubt the geometry is more relaxed, but maybe too much - several degrees may push things too far the other way. It is pretty heavy too, and certainly not an XC frame.

captainfly

Is that a layback seatpost?
An inline one with the saddle futher forward with a little bit more nose down angle. And stiffer forks will feel better.

rudedog

captainfly wrote:

Is that a layback seatpost?
An inline one with the saddle futher forward with a little bit more nose down angle. And stiffer forks will feel better.

no - pretty sure its a raceface evolve xc

captainfly

rudedog wrote:

captainfly wrote:

Is that a layback seatpost?
An inline one with the saddle futher forward with a little bit more nose down angle. And stiffer forks will feel better.

no - pretty sure its a raceface evolve xc

Which has about 20mm rear offset iirc, either way with that seat tube angle it does move the rider further back, the saddle is pushed all the way forward and still looks hung out over the rear wheel.

duke duvet

Hmmm. I know how you feel!

I've got a GT Zaskar Pro (07). It came with a 110mm stem and riser - the reba fork has 85mm travel. I fitted a 90mm stem and fire xc pro tyres for a more trail friendly set up .

Around Glentress on the blue and red routes the handling has led me to having a few offs. It has the same jack knifing traits as you mentioned, even on the uphill hairpin turns - the front end just suddenly digs in and your off. The other problem is front wheel wash out. I have ridden exactly the same trails on various bikes - Giant Anthem X2 & Reign, Genesis Ti, Kona Caldera and I had no problems with any except the anthem on tight uphill turns, which has the same racy angles as the Zaskar.

With a flat bar and longish stem the Zaskar is much better, it seems more of my weight is over the front tyre and everything feels more balanced.

Maybe your problem is about "old skool" set up and trying to moderise it as Steve b suggested. That is exactly what I tried and it just seems too compromised. A Genesis or the Cove might be a good bet for you. But go and test some bikes at a demo day I learned loads being able to compare bikes as to what suited me best.

Hope this helps.

BG2000

Thanks everyone for the advice.

Duke, your description sounds very familiar too !

Anyway, I couldn't resist temptation, and bought a 17.5" Cove Stiffee frame on Friday, swapped everything across from the old bike (apart from seatpost) and drove up to Dalby Forest first thing Saturday morning. I met some mates and we rode non stop for 7 hours ! The trails (all red and black) where amazing, and I totally recommend this place.



The new frame was a great success. Straight away, if feels more stable when cornering, and most importantly, predictable. The front end just goes wherever you point it, at all speeds, no matter what the surface.

It's also better on climbs. I could ride up the inside of steep hairpin bends without the front wheel rising and skidding away.

It absorbs bumps better, but is stiffer and more responsive at the same time. I'd say the bike is about a pound heavier now (approx 27lb) which is hardly noticable. Still much lighter than my mates full suspension bikes, so I was waiting at the top of every climb for them !

Regarding angles, my bars are at the same height, as I just used 2" of spacers to pack out the extended steering tube. I won't cut the steering tube down as I don't want to lower the bars. I reckon with my 100mm forks, my seat angle is slightly steeper, which may explain why it's climbing better, and feels better on very rough downhills.

In the end, I'm glad I got matt black. Very stealth like. Isn't it lovely when you buy a top end item, and it just feels sweet !!!

nicklouse

for fun.

BG2000

Hey, nice piccie - I never actually saw the disc version of my bike, but remember it was £300 more.

Mine came with Avid Single Digit V-brakes. I had to purchase a chainstay to IS adaptor plate from A2Z in the USA to get a rear caliper installed. I did this when my old Dolomite wheels wore out and I changed to Mavic disc wheels.

What's odd is that the rear caliper in your photo appears to be mounted above the dropout. On my frame the adaptor bolts are on the chainstay. I wonder why the disc version would use something different all together ?

That's clearly the 17.5" frame - the one I should have got !!

flo411

BG2000 wrote:

The new frame was a great success. Straight away, if feels more stable when cornering, and most importantly, predictable. The front end just goes wherever you point it, at all speeds, no matter what the surface.

It's also better on climbs. I could ride up the inside of steep hairpin bends without the front wheel rising and skidding away.

It absorbs bumps better, but is stiffer and more responsive at the same time. I'd say the bike is about a pound heavier now (approx 27lb) which is hardly noticable. Still much lighter than my mates full suspension bikes, so I was waiting at the top of every climb for them !

Regarding angles, my bars are at the same height, as I just used 2" of spacers to pack out the extended steering tube. I won't cut the steering tube down as I don't want to lower the bars. I reckon with my 100mm forks, my seat angle is slightly steeper, which may explain why it's climbing better, and feels better on very rough downhills.

In the end, I'm glad I got matt black. Very stealth like. Isn't it lovely when you buy a top end item, and it just feels sweet !!!

Hello,
I am late in this topic (and my English is not fluent, sorry)
But I have a question for you.

I actually ride a Treck 8500 like you (19.5 and full xt), and I would like change for a Cove stiffee frame (17.5) with a 140mm fork.

But, I would like knowing if this travel fork is not too large for climbing?
I live in Belgium and I have to climb frequently before small (but funny) downhill.

Thank for your attention