Random idea for front forks.

For various reasons too boring to go into, I've got a spare set of Chromoly front forks for a quill stem, 26" wheel.

One of our kids bikes is a small framed aluminium fishtail. It's okay, but all the boys say the suspension forks raise the handlebars too high and make it a less comfortable ride. As the frame is smaller than my 18" MTB and the handlebars are higher than on my bike, I can well understand this. Both boys who have grown big enough for an adult bike say the riding position is vastly improved.

I'm wondering how feasible it would be to swap the suspension forks -which are no-name forks that you'd expect on a kids bike anyway, with the cromo forks.

Is this even possible, and if so, what are the critical points to measure to see if I have a chance of making it work?
 

rogerzilla

Legendary Member
This is a can of worms but you might get lucky. The head angle will steepen with shorter forks so ideally you need less offset to prevent the steering being too twitchy. It depends what the steering feel is like at the moment.

If the child's bike has an A-head, you'll need a new quill stem and threaded headset to replace the threadless ones on there.

Steerer length needs to be sufficient to fit the headset. A bit too much length can be packed out with spacers. A lot too much should be cut down BUT you still need to have thread showing all the way down to the head tube. Threading can be extended by a really good bike shop but it's expensive.

I'm assuming both forks are for 26" wheels, yhe same type of brake and the same steerer size.

If all is good, you still need to swap the crown race between forks. It is not easy to seat a traditional non-split crown race without the right tool (a very heavy steel tube that just fits over the steerer)
 
This is a can of worms but you might get lucky. The head angle will steepen with shorter forks so ideally you need less offset to prevent the steering being too twitchy. It depends what the steering feel is like at the moment.

If the child's bike has an A-head, you'll need a new quill stem and threaded headset to replace the threadless ones on there.

Steerer length needs to be sufficient to fit the headset. A bit too much length can be packed out with spacers. A lot too much should be cut down BUT you still need to have thread showing all the way down to the head tube. Threading can be extended by a really good bike shop but it's expensive.

I'm assuming both forks are for 26" wheels, yhe same type of brake and the same steerer size.

If all is good, you still need to swap the crown race between forks. It is not easy to seat a traditional non-split crown race without the right tool (a very heavy steel tube that just fits over the steerer)
Thanks for that.

Both bikes are 26" wheel, quill stem, V-Brakes. Otherwise I'd not even contemplate this.

It looks like it won't be possible to measure beforehand and I'll have to just pull the current forks off and check things like the stem diameter. Will have to think about this one....

I'm hoping that the shop employing Elder Son has a crown race tool. That said, when I was young and foolish I once swapped a set of forks on a bike without changing anything and the bike is still in use today...
 
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rogerzilla

Legendary Member
The threaded steerer will be either 1" (most common) or 1 1/8" (common on late 80s/early 90s MTBs, and still used on Bromptons). They look very different. If any quill is protruding, it will be 22.2mm to fit into a 1" steerer or 25.4mm to fit into a 1 1/8" steerer. If you do the maths, you'll see that steerer tubes are 1.6mm thick where the stem inserts...they are not allowed to fail!

The thing that's most likely to be a problem is steerer length. It's easy to measure the head tube of the bike without any dismantling. Then measure the steerer of the rigid fork. If it's about 40-50mm longer than the head tube, that's ideal. If it's 30.5-40mm, you *might* need a lower stack headset. If it's less than 30.5mm, no headset I know of will fit.
 
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