AST236

I picked up a Diamondback Apex SE as a knock around bike. Great frame and everything is in pretty good shape except for the suspension fork. It's toast, which is fine because I want to replace it w/ a cro-mo rigid fork. Can someone point me to something w/ the general dimensions to assure that my ride height/attitude is correct.

I will probably cut the steerer tube a little tall and use spacers because I may do a drop bar or mustache bar conversion and could use the extra height.

Oh, and it's a 1 1/8 threadless........

Thanks.

BCRider

You want the measurement from the top of the crown headset race to the dropout mouths to measure roughly the same. But don't measure the existing fork when unloaded for this or you'll get an over long measurement. Instead lean up against a wall and assume the sort of stance you have when riding and have a buddy measure the distance when compressed. THAT is the measurement you want to come close to copying.

There's a wider variety of rigid forks out there these days simply to deal with the wider variety of short to medium travel suspension forks. So do the measurement yourself and then go shopping for choices.

fietsbob

+1 .. Sit on the bike , have someone else measure it .. preload sag can be compensated for then.

rake /offset is another dimension to learn .. but that may be irrelevant if you just take what you can find

in the low end of the market .

dabac

You're not saying in which way your current fork is "toast". Air sprung forks that fail completely usually sink to their most compressed position. If that is the case, it'd be hard to get a sensible axle-to-crown out of it.
OTOH, if you're happy with how the bike handles at that state then there's nothing stopping you from getting a rigid fork in that length. Coil spring forks can seize solid at pretty much anything between full extension and full compression.
Ideally the fork still works pretty much as expected, in which case getting on and measuring the ATC will give a good value for a replacement fork that won't change the handling that much.

AST236

Yeah, this one is completely shot and is resting in it's compressed state. I'll take it w/ me next time I make it down to see my friends at the nearest co-op and let them help me measure. Maybe I'll get lucky and they'll have one in the take off box......I don't mind spending the money to get the right one, but I want to be reasonably sure I'm getting what I need when I order. I think it's a Manitou Comp 5 suspension fork on there now. Maybe I can find some info on their website.

After my coffee, I'll take a look......

Thanks for the answers and the help.

Frank

mconlonx

What travel distance was the bike's fork marketed? There are various rigid forks which will match that marketing, i.e. 80mm or 100mm suspension corrected. You could also worry about the offset if you really want to...

dabac

Well, if you're happy with how it handles now, no need to look for any other length.
Or, if the fork can still be "exercised", ie pushed/pulled from full compression to full extension, then you can work out the travel. And from full extension you can then work out an approximate ATC. A common recommendation is that you should have 25-30% of "sag". Meaning that if you have 100 mm of travel, the fork should sink 25-30 mm when you're on the bike. Don't worry if your measurement ends up being a little odd, there's usually a rubber bumper at both ends that are actually part of the travel. And you can't pull hard enough to compress those to get the travel out.