Bicycle Mechanics - Concerns about Changing from 80mm Fork to 100mm travel

I just replaced the Manitou Axel, 100mm travel, fork on my 05 Rockhopper. So now I've got a used Manitou Axle hanging around. I've got an old, about year 2000 or 01, Hard Rock beater MTB that I'm rebuilding. The Hard Rock has the original SR Suntour 7700, spring fork about 80mm travel. I know the Axle is an entry level fork, but with oil damping and heavy duty springs that were installed, it has to be a big improvement over the Suntour fork.
My question is, how will the increase of 20mm (or more) in the travel affect the handling of the Hard Rock? Will it change the geometry of the bike so that the handling degrades or will there be little or no effect? Has anyone else made a similiar change?
Thanks for your input.

Not exactly what you asked, but isn't there a way to reset the Axel to 80mm travel?

BTW, what fork did you put on the Rockhopper?

Not exactly what you asked, but isn't there a way to reset the Axel to 80mm travel?

BTW, what fork did you put on the Rockhopper?

Thanks for asking BluesDawg. I'm going to a (used '04), Fox Float 100 RC. I'm real anxious to try an air fork on the old Rockhopper and lose that 1.5 lbs off the front end.

I never thought about changing the travel on the Axel, I don't know how to do that or if it can be done. But like everything else, if that's the way to go, I'll learn how. If it doesn't make a difference, I'd rather keep the travel at 100mm.

roccobike, I've not done that switch on any of my bikes, but I've known folks who've gone from 80mm to 100mm travel. No noticeable handling problems that I know of, just a plusher ride. Actually, I'm pretty sure I've seen identical frames that were available with 80mm or 100mm travel, depending on the specific model of the bike.

What you might do is check the axle to crown measurement of the two forks and see what the difference is. It might not even be 20mm. One thing about it, you'll probably set the longer travel fork up with more sag than the shorter fork, so the net difference won't be a full 20mm even if the axle to crown dimmension is 20mm different..........This is making my brain hurt. I think it will be fine.:D

Thanks well biked, I measured the axle to crown on both forks. The Manitou Axle is 20mm longer. That's a good point about the sag, there's going to be variation no matter which fork is on the bike. As a heavy rider, just over 200lbs, I will probably push the Axle fork down close to where a light rider might push the Suntour fork. I'm convinced. I'm going to go with the Axle.
As I said earlier, the Manitou Axle may not be high end, but it's WAY better than the current Suntour fork on the Hard Rock.

I have a 2005 Trek 4300 that I changed the stock 80mm fork to a Rock Shox Dart 3 100mm travel and it made a big improvement in handling. The added adjustment of the 100mm fork made for a softer ride.

I have a 2005 Trek 4300 that I changed the stock 80mm fork to a Rock Shox Dart 3 100mm travel and it made a big improvement in handling. The added adjustment of the 100mm fork made for a softer ride.

Thanks, That's what I wanted to know.

You already got your question answered, but I just bought a frame (Yeti ARC) that says it's built for a 100mm travel fork and put my 84mm (?) travel RockShox SID on it and it handles fine. Angle wise, that's pretty small. If you were going to a 150mm travel fork it might make a significant difference but in your case it's pretty small.