Frame Size | Small | Medium | Large | XL |
---|---|---|---|---|
Seat Tube (centre-top) | 15.35” | 16.7” | 18.1” | 19.5” |
Top Tube Length (Effective) | 23.6” | 24.6” | 25.6” | 26.8” |
Head Angle | 66.0° | 66.0° | 66.0° | 66.0° |
Seat Angle | 75.0° | 75.0° | 75.0° | 75.0° |
Chainstay Length | 17.5” | 17.5” | 17.5” | 17.5” |
BB Drop | 2.35” | 2.35” | 2.35” | 2.35” |
Head Tube Length | 3.9” | 4.3” | 4.7” | 5.1” |
Reach | 17.3” | 18.1” | 19.1” | 20.2” |
Stack | 23.6” | 24.0” | 24.4” | 24.7” |
Wheelbase | 46.1” | 47.1” | 48.2” | 49.4” |
Maximum Seatpost Insertion (including actuator mechanism) | 251mm | 286mm | 321mm | 356mm |
apologies missed the question in the earlier post and it's indeed a very good question.Thing is I want to know what it would be if you altered the old bike, 26 er an 40mm /390 rigid forks.
That's alters a bike , so geometry has to change to cater for the changes, 29ers wheelbase has to be longer to start with, the front end has to be higher, the forks longer so everything changes, with the front being higher, your stance is different so it all changes again.
You seem to know what the charges are, so what would a modern short travel 26er be from BiTD under new geometry.
So a stem shortens from 135 (standard/short back then).
To what 80mm, so we loose 2" or so, so TT can take that. Etc...?
Thing is I want to know what it would be if you altered the old bike, 26 er an 40mm /390 rigid forks.
That's alters a bike , so geometry has to change to cater for the changes, 29ers wheelbase has to be longer to start with, the front end has to be higher, the forks longer so everything changes, with the front being higher, your stance is different so it all changes again.
You seem to know what the charges are, so what would a modern short travel 26er be from BiTD under new geometry.
So a stem shortens from 135 (standard/short back then).
To what 80mm, so we loose 2" or so, so TT can take that. Etc...?
oooh ... I forgot seat tube length ... you're right ... go to 12-13 inches for the seat tube.I think @2manyoranges has gone a bit further than I would on some of his numbers. With rigid or very short travel fork, you’re not getting any head angle steepening to any degree as the fork goes through its travel. I’m running nearly as much sag as a 40mm fork has travel. Head angle changes by 0.5° for every 10mm travel, so 40mm travel it will only alter 2° max and for very short periods. I think 67-68 would be more reasonable.
My hardtail had 130mm forks and so changes head angle up to a maximum of 6.5°, so it needs a slacker starting angle.
Seat tube angle needs to be steeper on full suss as it reduces under sag. Hardtail 76° max would be enough.
80mm stem is huge these days, I’ve nothing over 50mm and some as short as 35mm. Less slack bikes can get away with a bit longer, so I’d say 50mm.
Agree with longer head tube, IMO a better option than more rise on the stem.
Definitely need more length in the bike both in the front centre and chainstay length.
Lots of stand over and short seat tube to allow for 200mm dropper post.
Can’t give exact dimensions and I’m not even convinced those changes would work. Bike handling doesn’t hang on one or even two numbers, it’s a blend of everything. You need slacker head angle to compensate for increased travel. Steeper seat angles to help weight the front of longer bikes. I don’t think a 40mm travel 26” bike would have to evolve so far.
Not going to paste the whole thing but here’s the link to the Chameleon archive with geometry if all the versions.
https://www.santacruzbicycles.com/en-GB/archive/bike/chameleon
Please do, everyone’s tuppence welcome.Like a good geo thread. I was going to contribute with pre-80s Road / MTB stuff,
I'm out of my league and will sit back and try to learn something.