What have I done to my bike???

Joeblack

Hi guys,

I know this is going to be difficult but you never know it might be something obvious or just me taking a bit to get used to the bike set up this way who knows!!!

Any way here goes,

Today before I went out I wanted to try the set up of the bike slightly differently, so I dropped (and flipped) the stem one spacer down the headset, levelled the bars slightly, pushed the seat backwards slightly also I pumped the tires up to 115psi (thereabouts) I did this to give myself a lower profile on the bike to see how it felt over a short distance, position wise it felt good, I had no problem getting low over the bars but whilst in a normal upright riding position the bike felt very twitchy ESP when turning the bars slightly

Any obvious reason why this may be?

Thanks for the help

mifkif

I would suggest, reverting back to the original set up and then change one thing at a time. At least that way you can work out which element is causing the bike to become twitchy.

Matt

Drumlin

At the risk of asking the obvious, is the headset properly adjusted ?

Joeblack

Drumlin wrote:

At the risk of stating the obvious, is the headset properly adjusted ?

State the obvious by all means, I'm relatively new to all this, what do you mean by properly adjusted?

nicklouse

you did refit the spacer above the stem.

Joeblack

nicklouse wrote:

you did refit the spacer above the stem.

Yes did that, as iv only had the bike two weeks and the tires came pumped up from the lbs it's the first time iv ridden it since they've been at a correct pressure could that be it?

Joeblack

mifkif wrote:

I would suggest, reverting back to the original set up and then change one thing at a time. At least that way you can work out which element is causing the bike to become twitchy.

Matt

Yes thanks, I think this will be the next step

ed_j

Joeblack wrote:

nicklouse wrote:

you did refit the spacer above the stem.

Yes did that, as iv only had the bike two weeks and the tires came pumped up from the lbs it's the first time iv ridden it since they've been at a correct pressure could that be it?

You'd be amazed at how much pressure 700C tubes lose overnight. You were probably riding at very low pressure if you hadn't pumped them up for two weeks.

Joeblack

Yes when I finally got a pump with a gauge they were very low, would going from low to correct pressure make the bike feel twitchy to me?

Also looking at other threads iv pumped both tires to 115psi and that calculator (posted in another thread) says it should be 120back and 80front

hipshot

Yes. Sounding very much like it's the tyre pressures. You dont have to max out on the pressures, especially at first.

Kudos on dropping and flipping the stem btw 8) .

Joeblack

hipshot wrote:

Yes. Sounding very much like it's the tyre pressures.

Kudos on dropping and flipping the stem btw 8) .

Ok great at least I know I havnt ruined the bike (although I don't know how any of that would have)

And thanks 8)

confused@BR

Plenty of good advice already but the 'incremental changes' approach can work for us as well as B C. I am assuming that the bike is new which usually means that the tyres are of low quality with poor grip. You have, probably, over inflated them, according to your weight 100psi is usually a good compromise, with the front tyre 5 or so psi less than the rear which takes most of the weight.

Just because the tyre wall says '115psi max' it is not a direct order. Lower pressures are worthwhile in the wet as well.

Joeblack

confused@BR wrote:

Plenty of good advice already but the 'incremental changes' approach can work for us as well as B C. I am assuming that the bike is new which usually means that the tyres are of low quality with poor grip. You have, probably, over inflated them, according to your weight 100psi is usually a good compromise, with the front tyre 5 or so psi less than the rear which takes most of the weight.

Just because the tyre wall says '115psi max' it is not a direct order. Lower pressures are worthwhile in the wet as well.

Ah ok, I'll drop the tire pressures accordingly and give it another go tomorrow,

The tires are sh1t, new ones have been ordered

craker

If you've taken a headset spacer out from underneath the stem, perhaps you ought to put it back on top of the stem - this is because the steerer tube may be too long to allow you to tighten the headset without the spacer in.

Imagine if the steerer tube on your fork was really long and protruded well above the stem. In this case when you bolted up the cap all you do is bolt the cap to the steerer. Lift the bike up and the fork drops out.

Now what should happen is the fork steerer stops short of the stem. When you tighten the cap it hits the stem and pulls the fork up - this loads the bearings in the headset.

Is this clear? Others have noted it could be a loose headset. Put your front brake on and rock the bike backwards and forwards - if there's play in the headset you know what to do.

fast as fupp

best get tyres this time?

Joeblack

craker wrote:

If you've taken a headset spacer out from underneath the stem, perhaps you ought to put it back on top of the stem - this is because the steerer tube may be too long to allow you to tighten the headset without the spacer in.

Imagine if the steerer tube on your fork was really long and protruded well above the stem. In this case when you bolted up the cap all you do is bolt the cap to the steerer. Lift the bike up and the fork drops out.

Now what should happen is the fork steerer stops short of the stem. When you tighten the cap it hits the stem and pulls the fork up - this loads the bearings in the headset.

Is this clear? Others have noted it could be a loose headset. Put your front brake on and rock the bike backwards and forwards - if there's play in the headset you know what to do.

Yes I replaced the spacer,

Thanks for the advice I tried and there in no play in the headset,

I did however adjust the tire pressure today to 110psi rear and 80psi front and that seems to have done the trick I just took it on a quick 6mile blast and all was fine,

thanks guys

simon_masterson

Please don't be misled into using the 'max' rating on a tyre as gospel. They are just fudge numbers. The pressure you should use is determined by the combined weight of you and any luggage you might be carrying, the tyre and its size, the terrain you ride on and the desired level of comfort (though if you really care about that you'll be using a 28+ rather than a 23-25!).

As with many things, Sheldon Brown elucidates:

http://sheldonbrown.com/tires.html#pressure