New bike feels quite twitchy at speed

DodgeT

Normally an mtb'er, but got myself a carrera tdf a few months ago, just so I could get more rides in to improve the fitness. Ended up finding the love for road riding again and wanted something nicer, so bought a planet x pro carbon.
The ride of the px compared to the carrera is amazing, apart from 1 thing.. it is very twitchy at above 30mph on anything but very smooth tarmac.
Any speed on the carrera and it was fine, but not perfect roads on the px has me a bit nervous when the speeds get higher.
The main difference of cockpit setup is carrera has a 120mm stem (large frame) and the px has a 100mm (xl frame). Both feel very comfy and reach is virtually identical.
So im thinking, is it;
Shorter stem making the steering faster?
Lighter (its almost 4kg lighter) making the bike more prone to bounce of the road surface?
Me just needing to get used to it?
Or something else..

Thanks.

sigorman85

I had the same thing it just didn't feel the same but then there not the same bike it's what your used to i guess ....I went from a heavy bike down to the same bike as what you have but now that I'm used to it it fine

iron-clover

It could be a number of things- the PX might have a shorter wheelbase and have more 'snappy' handling than the Carrerra (you can feel this just generally riding so you can confirm/ rule this out).
I wouldn't have thought the stem length will make much difference tbh. Yes, the 100mm will make the handling more twitchy than the 120mm, but I've used both on the same bike and the difference wasn't all that much.

I find deeper rims (even as shallow as 29mm) to feel nervous if there is any kind of crosswind when the speed builds up, although I guess the wheels aren't that much different. Tyres make a huge difference though- the handling can change dramatically between heavy, worn tyres and light fresh ones, but I personally find it more of an effect at lower speeds tbh.

As you say, it might just be a case of getting used to it again- I've had a go on a friend's Carrerra tdf and found it to be fairly sluggish compared to my alloy Trek, and the PX is likely to be another step up.

danlikesbikes

Hard one to judge the cause but could be a few things or a combination of them.

On the speed side of things how's your weight are you on the drops or not, as I've found being on them gives me a more balanced weight and I find the front end a lot more stable.

Or could be tyre pressure either too high or right but making your lighter bike a bit more sketchy.

Or it could be your nervous and not that I'm suggesting your strangling your bars but perhaps you need to loosen up and let the bike go a bit, which might reduce the wobble and increase your confidence at speed.

diamonddog

The Pro Carbon is quite lively to ride but IMO this adds to the fun, it is a very responsive bike IME.
Mine has a 90mm stem on a small frame and it feels stable enough at 40mph on the descents I have done. I think you just need to get used to the feel of it.

JayKosta

If the bike starts to actually 'shimmy' at high speed then that's a problem.
But the steering being more 'twitchy' at high speed is probably due to its having lighter weight wheels and tires. The 'gyro effect' of heavy wheels and tires would reduce the about of twitch.

If you don't feel comfortable or safe, then just slow down a bit.... that's what I do - I like keeping my skin intact.

Jay Kosta
Endwell NY USA

gloomyandy

I had a bit of a moment on a steep hill with a very rough road surface on my PX pro-carbon (small). All got very twitchy and a big shimmy at one point. I've since ridden the same road a number of times on my Cervelo which is a similar size and setup to an identical riding position and that feels rock solid. Obviously different wheels/frame/tyres/everything but in this case the lighter bike handles better, so it is probably not a simple case of heavy v light. Having said that I still ride the pro carbon and it is a great bike, I' just a little more cautious on steep hills with poor surfaces!

stueys

Small changes in geo can make a significant difference to the feeling of stability on a descent. And part of the issue is that once a bike feels 'twitchy' you tend to be less relaxed which makes the difference even more pronounced.

Comparing my cervelo to my previous bike I found the cervelo felt much more stable on fast descents and less than perfect road surfaces. Main differences are a slightly longer wheelbase, a smidge less aggressive head tube angle and a touch more compliance in the frame. All fairly marginal but added together the cervelo feels much more stable north of 30.

andrewangus

I have had exactly the same issue swapping from exactly the same carrera to planet x.

Get rid of the AL30 wheel set for a start. I got campag Scirocco 35's and they have transformed the bike.

No more brake rub while climbing and loads more stable.

diamonddog

andrewangus wrote:

I have had exactly the same issue swapping from exactly the same carrera to planet x.

Get rid of the AL30 wheel set for a start. I got campag Scirocco 35's and they have transformed the bike.

No more brake rub while climbing and loads more stable.

Never had a problem with my AL30's after several years and a few thousand miles.

Baby Trek

I ride the track at Manchester and used to use their hire bikes. I then bought my own, a Planet X carbon and wow, what a difference. Twitchy is a very good word to use! It is so much more responsive than the heavier track hire bikes, you only have to think about changing direction and it does...if you actually try to change direction you will be off the track before you blink!
It has taken some getting used to and I suspect you have the same issue...different bike, different set up, lighter etc.

andrewangus

diamonddog wrote:

andrewangus wrote:

I have had exactly the same issue swapping from exactly the same carrera to planet x.

Get rid of the AL30 wheel set for a start. I got campag Scirocco 35's and they have transformed the bike.

No more brake rub while climbing and loads more stable.

Never had a problem with my AL30's after several years and a few thousand miles.

Maybe you weigh less than my 92kg bulk

fludey

I've just upgraded my felt 75 alu frame to a Planet X pro carbon...not sure id say it's twitchy but I would say it's very responsive and the steering feels very direct. Very little input required to change direction so it might be you just need to adjust and get used to feel of new frame.
Mine has 28mm semi aero wheels with flat pulled spokes and a 90mm stem, but I have always ridden 90mm stem.

diamonddog

andrewangus wrote:

diamonddog wrote:

andrewangus wrote:

I have had exactly the same issue swapping from exactly the same carrera to planet x.

Get rid of the AL30 wheel set for a start. I got campag Scirocco 35's and they have transformed the bike.

No more brake rub while climbing and loads more stable.

Never had a problem with my AL30's after several years and a few thousand miles.

Maybe you weigh less than my 92kg bulk

You are correct I do.

DodgeT

Some interesting replies there, common theme seems to be i'll get used to it

Out of interest I may well swap the stems over, just to see if that makes any difference. Other than that, will just have to ride more and get over the learning curve.

I came to work today on the carrera, it feels so planted. If only my PX could weigh the same but handle like the carrera, id be sorted

t4tomo

Are the tyres different? cheap stock tyres can adversely effect handling.

Wardster00

I had a similar issue with a Ribble bike. If you are using wheels with cup and cone bearings rather than sealed cartridge it may be that the cones need tightening up.

If they are shimano r500 they are probably cup and cone bearings.

Hope this helps.

on-yer-bike

You shouldnt have to get used to it. If its a good bike it will feel good straight away no matter how light it is. A friend had a pink PX, one of 5 road bikes he owned and he said the same. He sold it. Check the headset isnt lose.