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[Closed] Is My Geometry Maths Wrong?

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[#10598500]

I'm 6' 2" with a 32" inseam which puts me right between Large and XL on a lot of manufacturers frames. A paucity of demo bikes locally means I have to buy blind most of the time.

So, my last bike was a large. The manufacturer's website put me at the top end of Large. The seatpost etc felt fine but I did feel thrown over the front of the bike. On a coaching day the coach said he felt my bike was a little too small making it awkward to get into a stable ready position.

I did manage to sit on an XL frame of the same bike and with a 150mm dropper and 175mm cranks it felt much too big.

So, the large had a 19" seat tube with 150mm dropper and a 175mm crank. The XL has a 20.3" seat tube. I'm wondering if I bought an XL, fitted a 125mm dropper and 170mm cranks that should reduce the overall "height" by just over an inch giving me the same saddle to pedal distance but with a little added reach?

Is that too simplistic?


 
Posted : 25/04/2019 11:06 pm
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Reach is a frame dimension so you can't change it with any component changes apart from the length of the fork but you can change seat to bar distance by changing stem length and saddle offset ifthat's what you're thinking of.

It sounds though that you need a long bike but with low standover height. Just to compare I'm 3" shorter than you but have 1" longer inseam and have a frame with 470mm reach.

What are the reach measurements of the 2 frame sizes and what saddle to BB centre distance do you need?


 
Posted : 25/04/2019 11:24 pm
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In proper terms, 482mm for the L and 515mm for the XL. What's the bike?

I'm 6ft 3in and ride an XL, with a 523mm seat tube length and 170mm cranks, and have a 150mm dropper with around 45mm of post showing under the collar. That's on SPD's so you gain a few mm from them.

You'd probably still be able to fit a 150mm dropper even with the 175mm crank.


 
Posted : 25/04/2019 11:30 pm
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Sounds about right to me. The XL bike will have more reach. On the one you tried was the dropper fully inserted in the seat tube?


 
Posted : 25/04/2019 11:30 pm
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A lot of bikes are being made with shorter seat tubes now for exactly this reason - you can size up for longer reach without it being too tall.

I'm similar height to you with longer legs but both my bikes have 2-3" of space to lower the seatpost, even with a 150mm dropper on one. I think your idea would work but if it involves buying a new frame, dropper & cranks anyway why not look around and compare the geo to some other bikes to see if you can find one that fits you better?


 
Posted : 25/04/2019 11:35 pm
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It’s an Intense Recluse.

Reach on large is 460mm and xl is 486. Thinking of fitting a 10mm shorter stem as well.

On the xl I tried I couldn’t get the dropper slammed all the way down. I’ve seen a few posts on other forums that folks found a kink in the carbon seat tube on the recluse which blocked the seat post from being fully inserted.

Previously had a Blur lt with 19.5 seat tube which I ran with a 125mm dropper and 170mm cranks. It was about as tall as I wanted to go.


 
Posted : 25/04/2019 11:42 pm
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I wouldn’t consider anything that can’t at least fit a 150mm dropper nowadays.


 
Posted : 26/04/2019 12:14 am
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Ha, I'm 5'9" and ride a long Pipedream Moxie and a large Knolly Fugitive. Try a brand with a shorter seat tube that allows more insertion. That large Intense would be too small for me.


 
Posted : 26/04/2019 5:27 pm
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same height and inside leg as you on a large Orbea Rallon with a 150mm oneup dropper.

My old large capra felt too small but anything bigger and i wouldnt have been able to touch the floor 😀


 
Posted : 26/04/2019 5:30 pm
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I'm your height and inseam.

I've made enduro bikes work for me from 432mm reach up to 483mm reach (limits of my experience so far). Important to note that I have raced down mountains at high speed at both extremes of this range and they both work.

Looking up the Recluse, the size L reach is 460mm. Modern thinking says this is at the low end of the range for your height but, as above, I've made both shorter and longer bikes work for me. There's a lot of nonsense about short stems that you have to ignore and just make the bike you have fit but at this point I'd have a preference in favour of the reach on the XL (486mm).

The XL seat tube length (515mm) is not the best. I went for a frame with a 510mm seat tube (too long really) but have managed to cram in a 185mm drop BikeYoke revive dropper. The BikeYoke was an expensive option but has a very shallow seal head and clamp so it ekes out the millimetres. There is a more mainstream 160mm drop version that would fit you no problem. Many other brands use much more space (Reverb is particularly bad) so make sure you get all the measurements before committing. The wrong brand of dropper would likely restrict you to 125mm drop.

If you can't get full insertion on the seatpost, all bets are off. On some designs the kinks in seat tubes are at the same height across frame sizes, so this can be very bad news. Getting hands on with the frame and your intended dropper is probably needed before dropping the cash.

I run 170mm cranks.


 
Posted : 26/04/2019 6:42 pm
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I also share your height and inseam measurements and have found that I just fit an XL Santa Cruz chameleon with a 150mm dropper. When I was looking around for a new hardtail I chose this one as it was likely the longest bike I could find that I could get a 150 mm dropper in. I am now running 170mm cranks and fairly fat (by modern standards) DMR V12 pedals but this allows me to be a whole 3mm off slamming my brand x post into the top of the seat tube. A one up dropper and/or a shallower saddle (mines is a fabric radius scoop I think) would likely increase this further if you wanted a little extra piece of mind/adjustability .

After all that fad, this is the first bike I’ve owned where I haven’t had to run a massive stem or push the saddle right back on its rails. It’s a nice feeling

I’ve demoed an XL high tower with a 150mm dropper and just got away with that too. Pretty sure it shares similar geometry numbers to the chameleon so is near the top of the list for the next bike purchase.


 
Posted : 26/04/2019 7:52 pm
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Thanks to everyone.

The kink in the carbon on the XL Recluse is not something I'm keen to start messing with. I can't help but feel there's a bit more carbon at that point on the seat tube for a reason.

Santa Cruz XL sizing looks spot on for me.


 
Posted : 26/04/2019 8:28 pm
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Just checked and the XL chameleon has a 490mm seatpost length and a reach of 487mm. So that should give a useful advantage over the intense XL sizing.


 
Posted : 26/04/2019 8:30 pm
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Cheers. After a full susser though.


 
Posted : 26/04/2019 8:41 pm
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Have you looked at some of the more progressive geometry (long, low, slack) bikes. Bird for example have reach 20-40mm greater than the set tube depending on the model/size. I wouldn't want to go back to a bike where seat tube > reach.


 
Posted : 26/04/2019 9:14 pm