I’ve tried to divine the reason from your comments, but I must have missed it – What do you think was the cause of this change?

I suspect it was because they were starting to get if you slackened the head angle and lengthened the front end it was better. Unfortunately they wanted to keep the wheelbase similar so they did their best to tuck the back wheel as directly under your arse as they could. Suddenly all the weight was on the back wheel if you used the same posture you had when front wheel was also closer. Cue front wheel washout hilarity.

While we’re on it, WTF is an athletic stance?

I linked further up the page:

I just figured out who I stole the athletic stance stuff from. It was @oliverdavey80

I see daveypushbikes.co.uk has disappeared which is a shame but you can still find his stuff cached if you want to look into more about his ideas on the Athletic Stance:

https://webcache.googleusercontent.com/search?q=cache:K6DbQ4CpSzQJ:https://www.daveypushbikes.com/blog/balancing-act-part-3&cd=1&hl=en&ct=clnk&gl=no

Basically it comes down to mechanical trail (for both the front and rear wheels) and wheel flop being the most important factors. And, of course, how these numbers change and the handlebar angle changes and the bike angle changes and etc… That’s what I mean by wheel size not being important for dynamics. Wheel size affects these numbers but it’s the numbers that are important from a dynamics point of view, not the size of the wheels.

Yeah I’m fairly comfortable with all those relationships within the limits of my maths, I have questions on how various combos that give the same trail or steering feedback might vary in some other respects in cornering, Qs that I can’t answer yet but all in all I think I get it. I appreciate that trail and flop can be the same across 2 quite different steering geometries and different wheel sizes and trail + flop is a significant part of handling feel. But I’d say wheelsize is an important part of the steering system because though you can have the same trail or flop numbers across 2 different OD wheels you can’t do it without adjusting offset and/or HTA, thf changing weight distribution between fork/bars and contact patch. For a bike ime/imo the starting point is weight distribution vs the wheels and range of rider movement or C of G, where small changes can be important in balancing it all up. We’re heavier than our bikes and can influence handling with our weight hugely.

Although you can have the same trail and wheel flop on 2 different wheel sizes, the radius of the wheel and the ‘cone’ it forms when cornering (assuming both tyres are same width) will be different, so there should be some change in handling influence there – one of the Qs that’s past limits of my mental model or maths though but I’d like to get the right model set up in CAD to look at it.

I’m not a motorbike chassis engineer (I’m not sure I’d describe myself as a bike designer as such, I work with a range of bike stuff inc frame designs) and I don’t know just how different the considerations there are. ‘A little knowledge is a dangerous thing’ etc.. But while I appreciate how trail and flop is important in bike handling and it can be balanced independently of wheel size, I don’t see how wheel spec can be separated out from steering, weight distribution, rolling efficiency, packaging and rider fit and so on when it comes to a bike design overall. It’s like the mistakes of focusing on head angle, or reach last year, or chainstay length a few years ago to sum up a bike – it’s all linked.

It could simply be that in the late 90s bikes were being built for people my shape and now they’re being built for people your shape?

Having said what I did about weight distribution, yes I think this is key. There will be a terrain chunkiness, bike + wheel dims and rider size balancing point for you that’s different for you than it is for someone well over 6′.

One one hand I’d say the wheels don’t care how tall you are, all that matters is mass and momentum and in that respect a bigger wheel can roll with less resistance – but where your C of G is and how (where) you can move about on the bike is also part of whether you feel like you’re flowing or not. Plough through Vs cut n paste sort of thing.

Don’t think I’d disagree with anything you’re saying, although I remember having the discussion with you about the contact patch cone shape for different wheel sizes before. I’m still a bit skeptical about whether the difference would be noticeable, tbh, but I’m prepared to be proven wrong 🙂

My main point is that there isn’t a ‘good’ wheel size or a ‘bad’ wheel size, even for use on the same terrain. If you wanted to keep the mechanical trail and flop numbers the same for a 26″ and a 29″ bike (through all bike and steering angles) I’m not even sure if that would be possible. I suspect not.

There are almost certainly some set ups that might not be possible on a 26″ setup but that goes both ways.

So yeah, wheel size is important but it’s just one factor in the main numbers we’re interested in.

We’re heavier than our bikes and can influence handling with our weight hugely.

Definitely. Also, as the wheelbase increases and the wheel size increases our ability to affect the handling with our weight shifts is reduced.

Again, there are positives and negatives to this. It’s going to come down the rider’s shape and weight and to personal preference.

It’s like the mistakes of focusing on head angle, or reach last year, or chainstay length a few years ago to sum up a bike – it’s all linked.

Again, definitely. Which is why I get annoyed when people say 26″ wheels make bikes bad. It’s impossible to reduce everything to a single factor, and some of us just tend towards a preference for smaller wheels and bikes that react more to our weight shifts.

Some of us real perverts even like 24″ 🙂

One one hand I’d say the wheels don’t care how tall you are

Indeed, I know people the same height as BruceWee on 29ers who’re happy. They may me making a trade-off between roll-over efficiency and handling, but that is simply one of many trade-offs we all make with our bikes.

My main point is that there isn’t a ‘good’ wheel size or a ‘bad’ wheel size, even for use on the same terrain.

Hmm.. I think that in some areas the negatives of small light wheels are so significant that they easily outweigh any benefits. For me, my 26er was slightly quicker on some steep smooth climbs than my first 29er, but I couldn’t actually get up some of the rocky climbs that characterise this area. It took me three goes to clean it, where I’d been doing it every time on the 29er. That’s a major downside. And even when I did clean it, it was a thrutchy mess rather than a good challenge.

In any case, my assertion wasn’t that 26 is bad, it’s that early 90s MTBs were bad. For people around my height I’ll stand by that! I think that the move to larger wheels forced geometry changes that were also beneficial for other reasons.

I think that the move to larger wheels forced geometry changes that were also beneficial for other reasons.

Definitely.

But I also think many people are mistaking correlation with causation and attributing improved dynamics solely to the wheel size change.