Homegrown hardtail differences?
If you look at the specifications of the '99 Homegrown, Homegrown Pro, and Homegrown Elite hardtails, they have 80mm forks. The other hardtails that year, and in the previous years, all came with 63mm forks. All the hardtails were listed with a 71.5 degree head tube.
So, did Schwinn tweak the geometry of those three '99 models for a 80mm fork, or do all the hardtails share the same frame geometry, and Schwinn just lied in the catalog (not unheard of)?
The models I'm specifically interested in are the '97, '98, and '99 models.
Well, I can't comment on whether the '99 models have different geometry for 63mm or 80mm forks. However, I have a '97 Homegrown that originally came with a 63mm fork. When it broke, I replaced it with a 2002 SID SL (bought used on ebay) that has adjustable travel (63 or 80). I've always ran it at 80 mm, and have been happy with the handling. So even if the geometry is a little different, I don't think that you'll have a problem with getting an older frame and installing an 80mm fork. BTW, the bonustomato website lists my 97 frame as having a 71.5 degree head tube also.
That's not quite why I'm asking, though. I have a Homegrown frame which came with a 80mm fork stock ('99 Homegrown Pro) which now has a 100mm fork, and I'm very happy how it rides. I'm trying to find out if the geometry was the same because that would mean I can run a 100mm fork on the previous years models as well, and they'd ride the same as my current bike. I have no interest in going back to a 80mm fork.
Crazy about Homegrowns
I'm in Boise right now, but when I get back at the end of the week I'll compare my 3 hardtail frames.
I have a 98 Control Tech, a 98 Factory, and a 99 Factory. From what I remember both Factory frames are exactly the same.
That is quite the collection you have there. It is a thing of beauty.
I was thinking of measuring the headtube in relation to the downtube. Think that would work?
OK, now I understand that you want to put a 100mm fork on an older 63mm frame. I also have an interest in this, although I'll probably keep my existing fork for a while.
If you look at the geometries for the 63mm and 80mm travel frames, you will notice that they all tend to have the same wheelbase, head angle, and bb height. This must mean that Schwinn has made some slight changes in the frame, since adding a longer fork will certainly increase wheelbase, raise the bb, and decrease the head angle.
Sheldon Brown's website has an article about calculating the effect of fork length on head angle: http://www.sheldonbrown.com/rinard/forklengths.htm
There is a list of fork lengths here:
Forks: Complete Axle to Crown Lengths Library
My frame is a 1997 19" Homegrown Hardtail XT, and has a 41.8" wheelbase originally. Thus, the head angle would be reduced by 2 degrees to 69.5. This will change the handling, but it's still in the "normal" range for an XC bike. Actually, a lot of people would consider this an improvement. It would be less an XC "race" geometry, and more an XC "trail" geometry to use marketing speak.
With the new head angle, you can calculate how much the front end lifts:
37mm * sin(69.5) = 34.7mm = 1.37"
The wheelbase should increase by 0.5" to 42.3":
37mm * cos(69.5) = 13 mm = 0.5"
The bottom bracket lifts by (approximation) the ratio of the chainstay length to wheelbase:
1.37*(16.7/42.3) = 0.54"
You won't notice a 1% increase in wheelbase, but raising the bb 0.5" will lift your center of gravity by the same amount. You may have to lean forward a bit more when climbing steep hills, but again it is a small percentage increase in the height of your cg. The new bb height is still within the "normal" range for an XC bike.
The impact on these measurements will be stronger on a 63mm frame than an 80mm frame, but I don't think it would be bad. It won't be the same as you 80mm frame, but I'm not sure how noticeable the difference would be.
Yeaaaaaaah...so let me tell you about Schwinn and their catalogs...
Originally Posted by WillTheGreat
Basically Schwinn not infrequently played fast and loose with the information in their catalogs. Just because it says their geometries are the same with different travel forks, doesn't mean they actually are. Schwinn could very easily have slapped a 80mm fork on there, said, "Meh, it's close enough", and saved the cost of changing the frame. Hence, I want to see any difference on actual frames.
Crazy about Homegrowns
Sorry I've been late in checking out my frames. I had a nice 4 day weekend waiting for me after my Boise trip, but it wasn't so nice since I got sick out in Boise. So my 4 day weekend turned into a 4 day "do nothing but try to get healthy" weekend.
I don't have any fancy measuring equipment, but it appears all 3 of my hardtails are the same. The 98 and 99 Factory frames are definitely the same. I also compared my 99 Factory frame to my 98 non-factory hardtail, which was more difficult because the 98 is built.
From what I can tell, they're the same.
I would venture to guess that Schwinn did exactly as you say, maybe they even realized they ride better with the bigger fork.
I really appreciate the effort, but the problem is all those frames came with 63mm forks, so you wouldn't expect any geometry changes between them. You'd really need to compare them to a '99 Homegrown, Elite, or Pro, which all came equipped with 80mm forks. I either need to get you a decent angle gauge, or put one of my frames in your hands.
Crazy about Homegrowns
99 Factory Catalog page. 80mm.
98 Factory Catalog page. 63mm.
Every hardtail in the 99 Catalog lists 80mm forks. Every hardtail in the 98 catalog lists 63mm forks. I'm starting to think Schwinn was lazy...
Yeah, you're totally right. It shames me I missed that.
So a comparison the '98 and '99 should show any difference in geometry. Hmm, I might need to send you an angle gauge...