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Author Topic: Oversteer on a bike that I haven't change then stem on???  (Read 2190 times)

DaveS

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Oversteer on a bike that I haven't change then stem on???
« on: 11, July, 2020, 10:35:33 PM »
I'm suddenly getting a lot of oversteer on my bike, i.e. bike feels like it would rather turn in either direction when you want to go straight.
If you keep your hands off the bars and bush the bike from the saddle, on straight ground, within a foot or two the wheel is at 90 degrees.

I have made a few changes lately but none that I think should be causing this.
  • I've changed the wheels, but re-tried the original front wheel but it made no difference.
    - I had changed the original wheel to tubeless while it was off the bike, so it's not exactly as it was, but again don't think it should make any difference.
  • I shortened the front brake hose a bit, but it's not very short and doesn't feel to me like there's any tention in it.
Could a really crappy headset cause something like this? (It's caged bearings rather than a sealed unit)
Anyone got any ideas?

DerMot

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Re: Oversteer on a bike that I haven't change then stem on???
« Reply #1 on: 11, July, 2020, 11:08:02 PM »
Sound like your headset could be going or gone, especially if it's been lying up. Open and check, but check for play first before opening. Tyre pressure could your next post of call but I think you'd notice that.

DaveS

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Re: Oversteer on a bike that I haven't change then stem on???
« Reply #2 on: 11, July, 2020, 11:32:40 PM »
Sound like your headset could be going or gone, especially if it's been lying up. Open and check, but check for play first before opening. Tyre pressure could your next post of call but I think you'd notice that.
The bike less than 2 months old and had only been to Ticknock a handful of times :(
Tried dropping the pressure in the front tyre a bit but didn't make any difference. Think I'll open up headset tomorrow :-\

DaveG

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Re: Oversteer on a bike that I haven't change then stem on???
« Reply #3 on: 11, July, 2020, 11:37:59 PM »
Did you try increasing the pressure?

DaveS

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Re: Oversteer on a bike that I haven't change then stem on???
« Reply #4 on: 12, July, 2020, 12:10:47 AM »
Did you try increasing the pressure?
I haven't yet. The change in steering isn't subtle so I'd be surprised if tyre pressure could be having this much effect. I'll give it a try anyway, I could be surprised!


UPDATE: I tried more pressure in both front and rear tyres separately. Adding pressure in front made it a lot worse, but think thats just because there is less tyre contact?
« Last Edit: 12, July, 2020, 02:57:02 PM by DaveS »

Hywel

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Re: Oversteer on a bike that I haven't change then stem on???
« Reply #5 on: 12, July, 2020, 01:09:55 PM »
Hi Dave, just to eliminate some things:
The handle bars are turning with the wheel?
This only happens when you are not on the bike?

I think your headset could be loose. This can happen on a new bike, as things settle in and get rattled around a bit. Can you try holding your bars and, while pulling the front brake, gently push the bike back and forth to see if there is any movement in the headset.

If there is movement, loosen off the side stem bolts one or two turns, then tighten the top cap bolt slightly and check for movement again. If you have the loose cage bearings be careful not to overtighten or you could pit the bearing race.

Don't forget to tighten the stem bolts again once you are done.

If that's not it, then....

DaveS

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Re: Oversteer on a bike that I haven't change then stem on???
« Reply #6 on: 12, July, 2020, 02:55:22 PM »
Hi Dave, just to eliminate some things:

I think your headset could be loose. This can happen on a new bike, as things settle in and get rattled around a bit. Can you try holding your bars and, while pulling the front brake, gently push the bike back and forth to see if there is any movement in the headset.

If there is movement, loosen off the side stem bolts one or two turns, then tighten the top cap bolt slightly and check for movement again. If you have the loose cage bearings be careful not to overtighten or you could pit the bearing race.

Don't forget to tighten the stem bolts again once you are done.

If that's not it, then....
The handle bars are turning with the wheel? Yes
This only happens when you are not on the bike? Nope, all the time

Doesn't seem to be any play in the headset.

Hywel

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Re: Oversteer on a bike that I haven't change then stem on???
« Reply #7 on: 12, July, 2020, 03:04:28 PM »
I'm stumped... Can you post a video? Sounds like you may need to get it checked out at the shop you bought it from.

DaveS

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Re: Oversteer on a bike that I haven't change then stem on???
« Reply #8 on: 12, July, 2020, 03:04:51 PM »
I've also tried the following, testing after each change:
  • loosed the brake lever completely, so there was zero tension in hose - no difference
  • changed the rear wheel back to the original - no difference
  • added pressure to rear tyre - no difference
  • added pressure to front tyre - made it a lot worse, but I think this is just due to less tyre contact
I haven't opened up the headset yet, as I'm haven't the time today.
I did look at the headset just after getting the bike and my first thought was that it belonged on a 200 road bike in the 80's, so will probably replace it anyway.

DaveS

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Re: Oversteer on a bike that I haven't change then stem on???
« Reply #9 on: 12, July, 2020, 03:10:41 PM »
It's hard to show you, but hopefully this will give you an idea???

[link removed]
« Last Edit: 18, August, 2020, 12:57:18 PM by DaveS »

Hywel

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Re: Oversteer on a bike that I haven't change then stem on???
« Reply #10 on: 12, July, 2020, 03:35:42 PM »
I'm going to say that's normal, so long as it's not doing that when you are riding and holding the bars, from what i can tell from that video anyway.

Take it for a slow spin around the block and see how it feels?

DaveS

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Re: Oversteer on a bike that I haven't change then stem on???
« Reply #11 on: 12, July, 2020, 03:45:01 PM »
Yeah, I've been doing laps of the block after each change. When cycling normally (on flat road) it feels like someone else has a hand on one side of the bars and are "helping" you steer. And that they're just waiting for you to drop your guard to they can teach you a lesson! :o

DaveG

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Re: Oversteer on a bike that I haven't change then stem on???
« Reply #12 on: 12, July, 2020, 03:50:15 PM »
Maybe the stem isn't aligned properly or the handlebars aren't centered on the stem properly?

Sent from my H8324 using Tapatalk


Hywel

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Re: Oversteer on a bike that I haven't change then stem on???
« Reply #13 on: 12, July, 2020, 04:17:52 PM »
Yikes! Take it back to the shop for sure, they should do it for no charge as it's new. Tell them to put a headset in that's from this century while they are at it

DerMot

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Re: Oversteer on a bike that I haven't change then stem on???
« Reply #14 on: 12, July, 2020, 04:33:33 PM »
Is it possible that this bike is slacker than previously owned bikes and that is what you are feeling through the handlebars? Slacker bikes will tend to wander more, feel like they want to steer themselves. That is until you get them up to speed downhill and they feel more stable. But you do say it only started doing it. Were you cycling another bike before this one, jumped on it and then felt like it was driving itself?

 

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