blawford

Around the beginning of lock down I bought a front mounted bike seat for our (now) 21 month old. It mounts to the steerer tube and has been great, it is mounted to my wife's GT Avalanche hard tail (it wouldn't fit my bike as the steerer tube was too short, thankfully hers isn't too girly!).

I have probably ridden it 20-30 times and recently the bike has felt worse and worse, to the point that I don't feel comfortable riding it. The feeling is hard to describe, but riding at speed in a straight line I can feel pressure through the handlebars that seems to go from one side to the other, like something isn't running true. Yesterday I took it for a ride on some gravel track and I felt like I was being pulled left and right at times, but after a bit of stop/start and swapping bikes with my wife it was much better sometimes than others.

The bike has been in an accident. It was on the back of our car when we got rear ended. The front wheel was buckled from the accident and was replaced with a new one. So this seems to point to some further damage, not sure what to check next though.

Given its intermittent nature I'm not sure if it could be anything to do with the positioning of our daughter in the seat? She weighs somewhere around 10-12kg, is fairly well restrained and doesn't seem to be moving about much when the bike feels weird.

Any advice or inspiration would be appreciated.

Bob the Mech

So the issue is with the GT Avalanche hard tail. With front suspension forks. Front wheel damaged and replaced. Adding weight forward of the bikes natural centre of balance high on the frame is likely to cause 'wobble' but this the issue happens with or without your child in the bike seat? Have you check for any damage to the sus forks, excessive play in the stansions and outer sleeves, cracks in the alloy crown or broken steerer tube? Is the alignment of the rear triangle of the bike ok...Check for cracks or breaks at the frame welds. In fact inspect everything, both wheels, handle bar stem.... It's unlikey that just the front wheel took a knock in the accident. And don't ride it...don't put your 21 month old on it...Seek the advice of a reliable local bike shop. Worst case scenario: the bike is a 'write off'...Best case scenario: The forks will need replacing.

dsaul

Sounds like the headset is binding. Does it turn freely from side to side or does it take some effort to turn the handlebars?

We don't realize it, but we are constantly leaning the bike back and forth while we are pedaling in a straight line and this causes the front wheel to turn slightly to each side, as we lean. If the headset is free to move, the bike corrects itself and continues to move straight ahead. If the headset is tight or binding, the rider has to constantly correct the steering to keep the bike moving in a straight line. It is a very disconcerting feeling and is a bit scary to ride at speed.

I would check the headset first to make sure its not too tight and then investigate possible bearing damage or a bent steerer from the accident.

blawford

Thanks for the replies. I finally got round to looking at this the past weekend. Nothing concrete to go on but one of the bearings does seem a bit miss-shaped, and there is a rough surface on the top of the fork where it looks like something on it.

The bearing is the caged ball bearing type and I am struggling to know what size I need, product information I found lists:

Headset - Integrated seal bearing, 1-1/8? Upper + 1-1/2? Lower.

Can you tell me what size I am looking for?

Bob the Mech

Integrated headsets will be fitted to the new models of the GT Avalanche. If you have caged bearing races, then they are not integrated seal bearing...yours look like this, yes?

If they do you will need 1-1/8 While you're pocking around the head set check for pitting and scaring on the bearing surfaces of the cups inside the head tube and on the fork crown race. If these are badly marked the new bearings will wear out pretty quickly.

HillRider

A front end accident severe enough to ruin the front wheel was also likely to have damaged either the headset or bent the steerer tube inside the headtube. I'd pull the fork and check the alignment and straightness of the steerer.

Bill Kapaun

Get a cheap caliper and measure.
Another way is line the individual balls against a ruler.
1/4" balls = 4 per inch.
3/32" balls = 8 per 3/4"
5/32" balls = 8 per 1-1/4"
Do the arithmetic for other sizes.
It's called thinking.
You can find them here- Scroll down a ways.
https://www.huskybicycles.com/headset-bearings.html

Trakhak

Given that you presumably don't want to endanger your daughter, stop asking people to guess what the problem is and take the bike to a bike shop for a thorough inspection.

blawford

So I am struggling here. Ball bearing size is 5/32" but the one I have infront of me has 33 balls. Outside diameter is around 50mm and I can find anything like that anywhere, most seem to be around 40mm outside with 20 something balls.

What am I missing here?

veganbikes

They did start out with a bad device to mount a child in front of them so while we hope they care about the life of their daughter it wasn't quite enough to put the child behind them where they are a bit safer.

Go to your local shop and get the bike looked at by a professional don't guess don't play around or just don't ride with any other passengers on the bike and please ride places away from other riders and cars so no accidents are caused. This is not the time to endanger peoples lives further this is a time where safety should be number 1.

If you are putting your kid in the front, then make sure you have a front loading cargo bike with a good safe area around them, belts and helmets. If you are putting them in the back use a proper child seat like Yepp Maxi or Topeak Baby Seat, something well regarded and safe. Avoid things that just clamp on to the frame or at least check with your local trusted mechanic and ask them if they would put their kid or partner on that set up.

I know in EuroDisney people love to mount children all over the dang bike but in EuroDisney they have had a cycling culture for a really long time and have a little more respect for cyclists and have a little more sense in terms of cycling. I am not condoning what they do as I do not think it is safe but it is slightly "safer" then doing it in a country that sees bikes as toys and cars as kings of the road.

blawford

I appreciate the posts on safety and I understand the moral implications of giving advice to strangers on the internet, but I am a very responsible person and of course my daughters safety comes first. The very reason I am posting here and not just riding around when something feels a bit iffy is due to that fact. Also we are talking about riding slowly on cycle paths here, not gunning it down a hillside, I won't be putting her back on the bike for anything other than a short test ride until everything feels 100% again.

Local bike mechanics are a bit hard to come by in the present climate, I have inspected everything and other than the bearing, everything seems fine. It is likely the headset bearing is a bit misshapen from when I fitted the bike seat as I found on a test ride that something wasn't seated correctly.

So, can anyone point me in the right direction for the part described in my last post?

ClydeClydeson

Look for cracks in the fork. Specifically, look around the area where the brake bridge connects to the lower legs.

Also look closely at the chainstays and seatstays, especially around the welded joints. A cracked frame or fork could cause the symptoms you are describing

blawford

Definitely nothing like that going on, I have given it a thorough inspection.

Now really just looking to find a replacement for the headset bearing.

Iride01 

Are you just guessing at a problem? I don't think the headset bearings will have any part in the symptoms you described in the OP. I'd rule out a a bent frame or bent fork first. And the bend can be so subtle you won't realize it without measuring and using certain tricks frame builders know to quickly see such.

blawford

Possible frame issues aside, the headset bearing is misshapen and needs replacing now I have removed it and I am struggling to find a replacement.

Iride01 

Bearing that's out of shape being the bearing cage as pictured in post #5 ? Just put loose balls back in. You don't have to fill the race completely with balls. If you do the math and understand the force vectors then you'll realize that having a gap for possibly as much as 20% of the radius circumference or even a little more is no big deal.

Just slap some grease on the race and stick the bearings in the grease. They should hold their position long enough for you to get it put back together. You've already gotten info on how to figure the size of bearings. If you use calipers, don't quibble about a few thousandths from what you measured the originals. You'd be better off removing the balls from the cage, lining them up, measuring and dividing.

blawford

I already have the size of the ball bearings 5/32", but at 33 balls with an OD of around 50mm I can't find anything similar to replace it with. Surely these things wear out and need to be replaced, I wouldn't really want to put the one I have back in given the condition it's in.

guy153

Just put loose balls in as Iride01 said. We always used to do this. Clean it out, fill it with grease and put as many balls in as will fit. I don't think the cages serve any purpose other than to make factory assembly quicker.

Without the cage there are more balls and they can move around more so it's probably actually better.