Sizing vs reach

Rusty_68

say no to ooogamaflap
Despite how it appears, I have nothing against older or used bikes, but whenever I'm looking there's never anything I want come up. Then when I've just bought something, finished building and am broke - it's time for @Rusty_68 to list exactly what I've been looking for for several months... :p
I wasn’t aware I had exactly what you’re looking for? If I do, let me know. I might list it for you?
 

beeb

Dr. Beebenson, PhD HA, ST, Offset (hons)
I wasn’t aware I had exactly what you’re looking for? If I do, let me know. I might list it for you?
Still at the broke phase, sorry! Disappointed I missed that Pyga to be honest (it was just after I got my Sentinel), that was a good looking frame. Johnny's a lucky man!
 

Rusty_68

say no to ooogamaflap
Still at the broke phase, sorry! Disappointed I missed that Pyga to be honest (it was just after I got my Sentinel), that was a good looking frame. Johnny's a lucky man!
I’ve never met Johnny’s partner, so I’ll take your word that he’s a lucky man.
 

Cardy George

Piercing rural members since 1981
So, should I be looking to get the next size down frame or not? I have a -17⁰ 70mm stem on the Procaliber and it nearly weights the front as much as I want. I'm old school, I like a sharp turn in, and while I don't want to go back to the old geometry, some preferences are hard to break. Will going smaller help here in Flatlandia?
 

beeb

Dr. Beebenson, PhD HA, ST, Offset (hons)
So, should I be looking to get the next size down frame or not? I have a -17⁰ 70mm stem on the Procaliber and it nearly weights the front as much as I want. I'm old school, I like a sharp turn in, and while I don't want to go back to the old geometry, some preferences are hard to break. Will going smaller help here in Flatlandia?
I keep wondering about your question @Cardy George... In theory, no - but that assumes riding in conditions with reasonable grip. But given you're also an inhabitant of Sand-sand-istan, things are trickier. Go too short and the front will wants to fold in the sand when turning. Not sure there's a clear answer in this case. For long straight runs it might be more stable, but not sure if that'll translate to corners. What stem length are you running currently?
 

Cardy George

Piercing rural members since 1981
I keep wondering about your question @Cardy George... In theory, no - but that assumes riding in conditions with reasonable grip. But given you're also an inhabitant of Sand-sand-istan, things are trickier. Go too short and the front will wants to fold in the sand when turning. Not sure there's a clear answer in this case. For long straight runs it might be more stable, but not sure if that'll translate to corners. What stem length are you running currently?
Lol, its probably not as sandy as you're imagining, it's predominantly loose over hard.

On a Trek sized M/L (18.5) I'm running 70mm, -17⁰. It came with a 70mm -6⁰, I tried 80mm and 90mm -6⁰ which helped pull the weight forward but dulled the response. The steeper angle lowered the bars and pulled weight forward without killing the edge but I still have trust issues. MOAR is always better ;). I (apparently) already sit quite upright compared to others so I'm concerned going to a shorter frame will exacerbate that. Should I try going with a longer -17⁰ stem?

The last MTB I rode with intent was a 1998 Trek Y11, and then I went to road bikes, so straight line stability is my lowest priority, I really want the thing to tuck in and turn.
 

beeb

Dr. Beebenson, PhD HA, ST, Offset (hons)
Lol, its probably not as sandy as you're imagining, it's predominantly loose over hard.
That's not much better! :p

On a Trek sized M/L (18.5) I'm running 70mm, -17⁰. It came with a 70mm -6⁰, I tried 80mm and 90mm -6⁰ which helped pull the weight forward but dulled the response. The steeper angle lowered the bars and pulled weight forward without killing the edge but I still have trust issues. MOAR is always better ;). I (apparently) already sit quite upright compared to others so I'm concerned going to a shorter frame will exacerbate that. Should I try going with a longer -17⁰ stem?

The last MTB I rode with intent was a 1998 Trek Y11, and then I went to road bikes, so straight line stability is my lowest priority, I really want the thing to tuck in and turn.
[Paragraph edited because my memory is bad - refer Post # 31 :oops:] - To be honest, this is on the periphery of my knowledge. But there are some points that resonate. For example, I know what you mean about the change in steering response from when I went from a 80mm stem to a 90mm, and it feeling kind of vague or ponderous. Sort of feels like your arms are trying to steer the bars into the corners, but your body mass feels like it's trying to push the bars towards the outside of the corner. 80mm (for me) felt more precise, but kept the weight on the front wheel in the old-school way. I'd wonder if going to a longer -17⁰ stem might still slightly risk some of those handling quirks of longer stems...?

In overall terms, if you were to downsize to a frame with shorter reach - I think it'd want to be a very small change (~10mm at most) or like you say you'll get sat even more upright (which will shift your weight back despite possibly putting more weight on your hands.

From what you describe, it sounds like you like the sizing and front-end response feel of your bike, but are just looking for more trust in the front tyre? (Which generally means you want more weight applied to that wheel)

One alternative worth considering if you're thinking about changing frames and the sizing of your current bike feels good other than lacking a little trust in the front-end, is to try and look for a frame with the same reach but slightly longer chainstays. That way you can setup your body position and steering response the same as your current bike, but you'll get more weight on the front wheel due to the change in weight distribution from the longer chainstays. A few mm at the back end can make a big difference in feel at the front. While it's all the rage to have shortish chainstays in modern XC, these are athletes that live in the pain cave as long as there's a performance advantage. Adding 3-5mm to the chainstays will weight the front wheel noticeably more and help the bike track a smoother arc through corners. The trade offs are it's harder to pop the front wheel up and onto steps and ledges (more noticeably when seated and grinding away, rather than standing where you can throw a bit more body langauge at it...). This sometimes an advantage or disadvantage in tight hairpins. Sometimes it makes the front harder to pop up and flick the bike around, other times it's good because you can get better grip if keeping the front of the ground. Food for thought anyway. :)
 
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Cardy George

Piercing rural members since 1981
That's not much better! :p


To be honest, this is on the periphery of my knowledge. But there are some points that resonate. For example, I know what you mean about the change in response when going from a 70mm to 80mm stem, and it feeling kind of vague or ponderous. Sort of feels like your arms are trying to steer the bars into the corners, but your body mass feels like it's trying to push the bars towards the outside of the corner. 70mm (for me) felt more precise, but kept the weight on the front wheel in the old-school way. I'd guess/suggest going to a longer -17⁰ stem might still retain those handling quirks of the 80/90mm stems, unless maybe you can find a 75mm stem and try to split the difference?

In overall terms, if you were to downsize to a frame with shorter reach - I think it'd want to be a very small change (~10mm at most) or like you say you'll get sat even more upright (which will shift your weight back despite possibly putting more weight on your hands.

From what you describe, it sounds like you like the sizing and front-end response feel of your bike, but are just looking for more trust in the front tyre? (Which generally means you want more weight applied to that wheel)

One alternative worth considering if you're thinking about changing frames and the sizing of your current bike feels good other than lacking a little trust in the front-end, is to try and look for a frame with the same reach but slightly longer chainstays. That way you can setup your body position and steering response the same as your current bike, but you'll get more weight on the front wheel due to the change in weight distribution from the longer chainstays. A few mm at the back end can make a big difference in feel at the front. While it's all the rage to have shortish chainstays in modern XC, these are athletes that live in the pain cave as long as there's a performance advantage. Adding 3-5mm to the chainstays will weight the front wheel noticeably more and help the bike track a smoother arc through corners. The trade offs are it's harder to pop the front wheel up and onto steps and ledges (more noticeably when seated and grinding away, rather than standing where you can throw a bit more body langauge at it...). This sometimes an advantage or disadvantage in tight hairpins. Sometimes it makes the front harder to pop up and flick the bike around, other times it's good because you can get better grip if keeping the front of the ground. Food for thought anyway. :)
You, good sir, are a legend.

Pushys have some stems on sale, might be worth the gamble.
 

SummitFever

Eats Squid
...I really want the thing to tuck in and turn...
Other thing to consider is how you have your fork setup. Corner grip is all about weight transfer onto the front wheel on corner entry. If your fork is set up too firm (either too much air pressure / compression damping / lockout / platform / stiction due to lack of mainteance / choose your poison) then the front won't tuck in nicely on corner entry. The secret to big amounts of front end grip is that smooth transition into loading up the fork with the cornering forces. If your fork is not plush enough, then adding more weight on the front end will just make the transition more abrupt and actually reduce dynamic grip at the tip in point.

To get a feel for this, lock your fork out and do some flat turns in a gravel carpark without leaning the bike in. Now unlock your fork and do the same thing. The "push" you get with the locked out/rigid fork is the thing you want to tune out.
 

beeb

Dr. Beebenson, PhD HA, ST, Offset (hons)
You, good sir, are a legend.

Pushys have some stems on sale, might be worth the gamble.
So, I went looking for a spare 80mm stem in the garage tonight for a mate's bike-path hybrid bike thingo.

Turns out my reservations about long stems do not include 80mm, aaaaaaaand that's actually the one I have installed on the bike currently. :oops: It was a 90mm stem I didn't like (in fact, I cut it up to make my push-up bars).

Oops...
 

k3n!f

leaking out the other end
Dear Dr. Beebenson,

I'm forever struggling with being between two sizes (M/L) as I'm 178cm tall. I'm currently on a medium SB100 with a reach of 432 and a top tube length of 605 which I ride with a 50mm stem. This is a pretty short playful bike that I ride in a fairly upright position. I have pretty long arms and legs, but a relatively short torso which was made even shorter with some thoracic spinal fractures a few years ago. I mostly ride XC style trails, but take the same bike away to Thredbo/Maydena/Derby and have been doing some 50km/100km races in the last 12 months.

According to Santa Cruz bikes, I'm in the middle of their large recommendation. On a Blur TR this would have a reach of 457 and a top tube of 621. On a Canyon Lux Trail I would be on a medium, although this is even longer with a reach of 460 and a top tube of 627. On the Epic Evo I am right between the M 436/602 and the L 460/629.

These bikes seem ridiculously long in comparison with my current bike, which I'm already running with a short stem. The M Epic Evo is the closest to my current bike (although the reach is a bit longer and the TT a bit shorter), but I don't want to stick with the status quo if I'm missing out on something. I am unable to test ride anything because of COVID before purchasing.

If I buy a bike that is 25-30mm longer in reach and top tube than my current bike am I making a mistake? Or is this long low slack thing going to be the best thing I've ever done?

Thanks,

Concerned Purchaser
 

leitch

Feelin' a bit rrranty
If I buy a bike that is 25-30mm longer in reach and top tube than my current bike am I making a mistake? Or is this long low slack thing going to be the best thing I've ever done?
What's your go-to saddle height, out of interest? Seat tube angle will make a difference as steeper STA frames can run longer reach for the same ETT giving you a longer front centre without stretching the seated position out.

I'm also 178cm, also typically in between M and L, but 432mm reach would feel tiny to me with a short stem. My current trail bike is size M 480mm R/626mm ETT, with 35mm stem, up from size L 455/626 on my previous w/ 50mm (slacker STA).

Sounds to me though that your back situation might be something to consider. I won't go for anything shorter than about 620mm ETT because the seated position feels too cramped, but I'm also quite flexible. I would not expect 25-30mm more in the reach to bother you at all, nor 20mm in ETT, but if your back can't do it, it can't do it.
 

SummitFever

Eats Squid
Because you're starting from a 50mm stem on your existing bike you can go to a 35 (maybe 32mm) stem on the next bike if you need shorten the reach a bit. Raising the bars or running a bit more sweep on the bars can shorten the cockpit up a bit too. I would go with the large. I'm only a couple of cm taller than you and I have never considered a medium. I think the better option is always starting with a bit more reach then you need and then sliding the saddle further forward / shorter stem to get the fit perfect.
 

Litenbror

Eats Squid
Because you're starting from a 50mm stem on your existing bike you can go to a 35 (maybe 32mm) stem on the next bike if you need shorten the reach a bit. Raising the bars or running a bit more sweep on the bars can shorten the cockpit up a bit too. I would go with the large. I'm only a couple of cm taller than you and I have never considered a medium. I think the better option is always starting with a bit more reach then you need and then sliding the saddle further forward / shorter stem to get the fit perfect.
My only thing to add to this is a word of caution with today's long, low and slack bikes. I have recently gone backwards from a 2019 large banshee prime to an short and steep Stumpy and found the short and steep much more playful. The prime was the better bike in almost every way and if I was racing, it would be the bike to use but it wasn't as much fun as the Stumpy. Today's bikes and geometry are much more efficient at going down hills quickly and as comfortably as possible and are much much more forgiving but, they might loose a bit of the fun doing it. It is a good idea to really know what type of riding you want to do, and enjoy doing, and make sure you don't end up with a long low sled that rides like a comfy armchair but may not give you that little tingle as you ride (you know the feeling, you fuck up a line and only just make it and think fuck that would have really hurt, then keep crashing down the hill at full speed regardless)

TL,DR consider modern geo but less travel to keep life and riding interesting.
 

leitch

Feelin' a bit rrranty
It is a good idea to really know what type of riding you want to do, and enjoy doing, and make sure you don't end up with a long low sled that rides like a comfy armchair but may not give you that little tingle as you ride
I totally agree in general, but take one look at @k3n!f's bike history and any of the rides he posts and you'll see he's at no risk of buying an armchair :p
 

beeb

Dr. Beebenson, PhD HA, ST, Offset (hons)
I'll try to remember to have a dig into your query when I get home @k3n!f - but I think the posts above are on the right track. If your current bike's geo is working well for you, you don't have to go radically different.

It's a struggle to try and offer sizing advice for shorter riders too, because for what I'd consider a "short chainstay" bike in my size, the same chainstay length on a size medium frame would offer weight distribution/balance to a long chainstay bike scaled up proportionally to my size.

Your usage case is tricky too. Because you're looking for one bike to ride all the trails, it really becomes a question of which part of the ride/terrain you want to favour.
 

k3n!f

leaking out the other end
I totally agree in general, but take one look at @k3n!f's bike history and any of the rides he posts and you'll see he's at no risk of buying an armchair :p
Indeed! If my back was still up to it I'd be on a hardtail.

Thanks for the replies everyone.

My saddle height at the moment is 76.5cm. I spent years riding with it 77.5-78cm but has lowered it to take some pressure off my lower back as I tend to ride longer distances these day. I've always found bikes end up feeling long because I have longish legs, so the saddle height gives me a longer effective TT. Interesting point about the STA and reach, although the SB100 at 74.2 is pretty close to the current "downcounty" standard.

It seems most of the information about reach sizing relates to standing descending ability and enduro style bikes. Given I spend 95% of my time riding XC the majority of time on the bike is seated and climbing, which seems like the effective TT length would be a better way of sizing a bike?

I need to think about this some more.
 

acads

Likes Dirt
Another 178cm rider here, it seems we are always stuck between M and L. I've split the difference and gone with a M/L! (Trek sizing, ETT 614/Reach at 461.
Previous bike was a medium Anthem which felt a little small but was very nimble, The Top Fuel is a little bigger but with a very different riding position as you sit in the middle of the bike. 60mm -13 stem -13 out of the box. I like the seating position as it's upright but I feel like I have a little too much weight on the bars otherwise it feels good. If you want to lift the front wheel you really need to mean it, where the Anthem just popped up easy. My riding is 95% XC and seated climbing.
Riding the large of the same bike was a no at ETT630/475R was a step to far.
 
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