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1,585 Posts
Discussion Starter · #1 ·
Thoughts comments please.

2018 stumpjumper 29/fattie. Vs 2016 Fuse fattie

ettl. Website says they are the same...

So i measure from the Top of headtube, middle along the side, back horizontally to middle of seat tube

Or Another way...

Set seat parallel to top of steerer. Measure horizontally from back of seat to center of steerer tube. Both bikes have same seat bars and placement in seat clamp.

Result 40mm difference???

head tube angle??
fuse has 27.5” auron boost. 495mm axle center to top of 35mm stanchions

jumper is yari 29 boost. 490mm axle center to top of 35mm stanchions.

(Could but havent removed wheels to get an actual axle to crown measurement)

Both forks are set for 150mm travel. Same tires and rims.

i deflated forks and shock to match ride heights at sag.

Results: Get 67.5 in jumper and 70 on fuse. Both are supposed to be 67.5

Note stock fuse fork was 120mm 29er boost and is long gone...

was running the auron at 130 initially as my lbs setup that way but it felt unstable and too steep. Heat tube angle with fork at full extension was steeper almost 68.5 if i recall. So i Then brought it up to 150mm and get about 67.5 at full extension. This felt much better and improved suspension action.

Should the hardtail measure hta of 67.5 at full fork extension or at sag???

3,825 Posts
The good news is that now you know that you need to measure your bikes if you care about performance.

The bad news is that now you know that what they sell isn't what you get.

Also, we don't use any top tube dimensions when sizing bikes and head angle is a second tier parameter.

mbtr member
6,503 Posts
You're comparing a suspension bike to a hardtail. Who knows under what circumstances spec is pulling the geometry from. The bent seat tube on the SJ just adds to the confusion, as does the overforking on the fuse. IMO hardtail and FS geo is just similar enough that drawing direct comparisons will lead to confusion with no easy explanation, and given all of the above a 40mm difference of ETT on identical fitting bikes seems plausible to me.

as pvd alluded to, you're bonus confusing it by taking measurements of features that are of secondary (or 0, for some) importance. I'd be more interested in comparing front-center dimensions between the bikes. When you're using a tape measure it can be much easier to get close enough by measuring the wheelbase. If the FC is close and the cockpits feel good... cool. You're better off addressing the handling of each bike on its own.

As far as measuring sag vs no sag... it's not worth doing AGAIN for this thread. No sag is easier to measure and sufficient for your purposes.

It might be more productive to ask 'hypothetically, what geometry tweaks would make my fuse feel more stable?"

1,585 Posts
Discussion Starter · #5 ·
The SJ is a new bike to me and i was just comparing setups to my fuse.

There arent alot of xxl bikes on the market and I've spent alot of time obsessing over dimensions only to find that manufacturers geo measurements cant be trusted anyway!

how are hardtails HTA measurements made: at sag with recommended fork or extended?

stock fork is suntour raidon 27.5+ boost 120mm (ac 523 from website)
was auron 27.5" boost fork (my lbs set at 130mm (ac 535mm)
now at 150mm (ac 555mm)

I measure 67.5 now. So how in the world did they get a HTA of 67.5 with a 30mm shorter fork? Maybe they had a special fork made for the fuse???

Perhaps this was the wrong forum to post in. Bike and Frame may have been better! So to post some actual creative content....

I built the following bike rack recently.
I have never welded aluminum.
A friend lent me the shop and materials and just said lock the door when your done!
2.5hrs later i think i did all right! just a little twist on the last one.

*Aluminum sure does pull!!!

Iron Composite material Steel Metal Daylighting
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