Deves

I would like to change the fork on my Motiv Spark from the standard fixed fork to a Mountain bike suspension fork. All I know is that the diameter is 1-1/8" and it's threaded. If the threaded tube is too long and I need to cut it how do I know how long to make it and how do I cut it without screwing up the threads? Is there a special tool needed for this procedure? Thanks

Deves

Nightdiver

You can of course try to go with the threaded suspension fork option, but there are some considerations there. First of all, I'm not sure if there are many (any?) quality forks offered with a 1 1/8 threaded steerer. If there are, then you hopefully are able to purchase one with as similar a size steerer tube as your current fork. If it's significantly longer you'll need to have a bike shop cut the fork and then cut in new threads. If only slightly smaller, then they would need to cut to length and then clean up the first couple of threads.

If it were me, I'd instead buy a standard threadless fork with matching headset, and a new stem. A little more upfront cost maybe, but opens up a much deeper pool of fork options.

slomoshun

Info here https://www.youtube.com/results?sear...a+steerer+tube

Doc_Wui

Are you sure you'll have a compatible fork? Very hard to cut more threads if there's not enough. This happened when I put a 1" suspension fork on my Trek 800. The tube on the new fork was 4 or 5 inches longer, and the thread ended about 2 inches above the frame. I had a die, but it was only for steel plumbing pipe and unable to cut the harder steel in the fork. When I learned a proper bike tool was over $100, I took the advice over in the mechanics forum and converted the fork to threadless. (No, they hate people like me at the local bike shops. No way I'm taking my bike/fork there.)

They also make a guide for cutting the fork thru the threads. I had to cut mine there anyway, and I used a sawzall and the old nuts as a guide. I recall that the nuts spun off afterwards, so if you're careful, you won't necessarily wreak the threads.

Ask over in the mechanics forum too.

Deves

Thanks for the input guys. I think I should go thread-less now just have to figure out what I need. The old bearings and races should fit on a new fork right?

Nightdiver

Not necessarily. Depends on the headset. I'd just swap out the whole headset while you're at it.

Deves

I went to the Bike shop where I bought my bike today and they had A motive Spark with a Rock Shox suspension fork setup complete with FSA headset and adjustable riser. It had a front disc brake adapter which I didn't know was needed. He has a guy that comes in and has already done a dozen of these conversions. It only takes about an hour.
He told me they can do the conversion for $400 which includes $350 for everything needed and $50 labor.

Doc_Wui

I think 50 bucks labor is a fair price.

Deves

Well I went ahead and had the bike shop do the fork swap and boy am I glad I did. There were a couple of things that needed doing that I wouldn't have been able to do without the right tools so that right there saved me money. Anyway the guy was in a little bit of a hurry as the shop was very busy and there were only 2 people working there. I waited a couple of hours while he worked on and off on my bike which was OK.
When I got the bike home I went over it and made a few adjustments. After assembling the front disc brake to the new fork the mechanic failed to run the brake cable around the bottom of the cable holder and had readjusted the brake so much that the brake pads were continually rubbing on the disc. I readjusted the cable and also the stem riser and handle bars to my liking too.
The bike now has the suspension it needed to soak up the bumps and make riding a lot more comfortable. And It also looks fantastic!