Size and Keeping Front Wheel Down

andy_welch

The Trance I have on demo is a great bike, but does have a slight tendency for the front wheel to lift on steep climbs. It is a medium size. Seeing me on it the guys in the shop thought I'd probably be better on a large (but didn't have a large size demo bike). What I'd like to know is whether going up to the larger size would make the front wheel more or less likely to lift up. Putting the front wheel a touch further forward should, I would have thought, help to keep it down, but then again, if it's further away it's going to be harder to get my weight over it.

Cheers,

Andy

bellys

Move you arse on to the front of the seat will help, or a longer stem but try moving your body forward 1st.
You can make a smaller bike bigger but not make a big bike smaller.

andy_welch

Thanks,

I can just about keep the front end down by shifting my weight (at least to the point where it gets too steep for me to ride). Just wondering whether a larger frame is likely to make the problem worse (or better).

Cheers,

Andy

chez_m356

andy_welch wrote:

Thanks,

I can just about keep the front end down by shifting my weight (at least to the point where it gets too steep for me to ride). Just wondering whether a larger frame is likely to make the problem worse (or better).

Cheers,

Andy

hard to say, but there must be a reason the guys in the shop thought you'd be better off with a large, it could just be down to your technique, maybe having a look on youtube for a few tutorials may help, would probably be a lot easier to find out if/where your going wrong that way

andy_welch

OK, I've had a look at the geometry chart on the Giant web site. Going from M to L the angles don't change and nor does the chainstay length, so it is just a case of the top tube getting an inch longer, putting the front wheel, forks etc an inch further away. Basic physics would suggest that should make it harder to lift the front wheel right.

Cheers,

Andy

The Northern Monkey

stand up?

IBISMojoHDamon

bellys wrote:

You can make a smaller bike bigger but not make a big bike smaller.

Couldn't disagree more....

Obviously buy the right size if you can, but if you are 5"ft 10" then you are borderline Medium / Large... I'd buy the large (assuming you have standover clearance) and fit a shorter stem.

IMHO, you can make a big bike smaller, but if you try to make a small bike bigger, it will mean a longer stem, thus putting your weight further over / towards the front axle (a bad thing as 150mm stems proved) or the seat further back on the rails (risking bending / snapping the rails) or using a set back seatpost, changing the centre of gravity from where it should be and putting the weight of you as a rider closer to / over the back wheel... making the front end light and wheelying everywhere...

A shorter stem (again IMHO, Giant use too longer stem on a large) would bring your weight / position back and give you more control on the downs, for climbs, you just need to shift your weight onto the saddle nose more (not completely) in order to keep the front wheel down.

I say all this as I am at the chiropractor once a week from riding a bike that was too small for me for years and knackering my back... Also a bike that's too small will result in your hands feeling pressured as more of your weight will be on them...

So, in conclusion, if you are 5ft 10" or more with 'normal' male body proportions, I'd go for a large... (without seeing you on the bike)

supersonic

So, in conclusion, if you are 5ft 10" or more with 'normal' male body proportions, I'd go for a large

Couldn't disagree more... Sizes vary so much, you look need to look at the full geometry, or simply test.

IBISMojoHDamon

supersonic wrote:

So, in conclusion, if you are 5ft 10" or more with 'normal' male body proportions, I'd go for a large

Couldn't disagree more... Sizes vary so much, you look need to look at the full geometry, or simply test.

And disregard what the guy's in the shop say that have seen him on a bike and recommended the right size based on their experience?.... It also mentioned 'without seeing him on a bike'...

supersonic

I'd test it, as I said, maybe elsewhere. Is impossible to say unless you understand the geo.

If he can't test I'd stick with the medium and make slight adjustments to riding style as it seems to work 'great' elsewhere.

felix.london

I don't see how a larger bike (longer top tube) will help keep the front wheel down on steep climbs. I would presume it would have the opposite effect, no?

I'm always bang on the cusp between M & L sizes (manufacturers on-line sizing apps or shop fitting) and I've always got on better with Medium's for climbing and Large's for descending

As others have said - the trick to steep climbs if you're front wheel is coming up is to shift forward as far as possible but stay seated so you are right on the tip of the saddle.

I had to 'master' ( ) this skill when I went from a 105-120mm fork and 110-90mm stem last summer.

Also letting some air out of your back tyre can help so you can put more weight over the front without losing traction at the back.

bennett_346

felix.london wrote:

I don't see how a larger bike (longer top tube) will help keep the front wheel down on steep climbs. I would presume it would have the opposite effect, no?

Thats what i was thinking

toasty

I don't see how a larger bike (longer top tube) will help keep the front wheel down on steep climbs. I would presume it would have the opposite effect, no?

The bulk of your weight isn't in your arms, smaller bike, will have a shorter wheelbase and you'll be running more seatpost, leaving you far more over the back axle. Weight too far back, front lifts up.

Bigger bike will have a longer wheelbase, you won't run as much seatpost so your weight will be further forward proportionally. Assuming no stem swaps and things, you'll be less upright on the bike too.

It's all down to weight position in relation to rear axle.

chez_m356

andy_welch wrote:

OK, I've had a look at the geometry chart on the Giant web site. Going from M to L the angles don't change and nor does the chainstay length, so it is just a case of the top tube getting an inch longer, putting the front wheel, forks etc an inch further away. Basic physics would suggest that should make it harder to lift the front wheel right.

i think this is where your going wrong, your analysing everything too much, you really need to just get out and practice, if there was some secret formula to it, then everyone would be a world class rider, but most of us aren't and never will be, its about ability not science, thats why one person can get up a hill and another can't, they are just better at it

andy_welch

chez_m356 wrote:

i think this is where your going wrong, your analysing everything too much, you really need to just get out and practice, if there was some secret formula to it, then everyone would be a world class rider, but most of us aren't and never will be, its about ability not science, thats why one person can get up a hill and another can't, they are just better at it

I'm sure there is some truth in what you say, but I'm not really asking for advice on how to keep the front wheel down (welcome though it is) I'm trying to decide which bike to buy and in particular whether the large size is likely to be even more prone to the front wheel lifting than the medium that I've tried. It sounds as though it's more complicated than I thought to predict this though. As you say, whatever I end up buying I'm sure I'll be able to cope by adjusting my riding position/style, but at the moment it's all about getting the best bike for my needs and right now it feels as though one that's a little less prone to the front wheel lifting on climbs would be better.

Cheers

Andy

supersonic

leaving you far more over the back axle.

I disagree (position wise), for a given rider, seat angle and chainstay length, you will be in the same place in respect to the rear axle as the bottom bracket to arse height will be the same. Just with more or less seatpost showing. However the actual weight distribution will be a little different. But the larger frame, with a higher headtube will tip your cog further back anyway, somewhat neagting that you have to reach a little further.

chez_m356

andy_welch wrote:

chez_m356 wrote:

i think this is where your going wrong, your analysing everything too much, you really need to just get out and practice, if there was some secret formula to it, then everyone would be a world class rider, but most of us aren't and never will be, its about ability not science, thats why one person can get up a hill and another can't, they are just better at it

I'm sure there is some truth in what you say, but I'm not really asking for advice on how to keep the front wheel down (welcome though it is) I'm trying to decide which bike to buy and in particular whether the large size is likely to be even more prone to the front wheel lifting than the medium that I've tried. It sounds as though it's more complicated than I thought to predict this though. As you say, whatever I end up buying I'm sure I'll be able to cope by adjusting my riding position/style, but at the moment it's all about getting the best bike for my needs and right now it feels as though one that's a little less prone to the front wheel lifting on climbs would be better.

Cheers

Andy

fair play to you, there's nothing wrong with wanting to make sure you get what's best for you, at least your out there actually trying the bikes

andy_welch

chez_m356 wrote:

fair play to you, there's nothing wrong with wanting to make sure you get what's best for you, at least your out there actually trying the bikes

Thanks mate. Not sure it's helping though I thought a test ride would answer my questions. Instead it just seems to have generated more. Good fun though.

I do wonder whether we (or at least I) am guilty of over analysing things when buying bikes. The Trance, for example, has been great. The more I've ridden it the more I've come to appreciate it. I'm sure if I got one I could have fun on it for many years to come. The amount of fun would, as always, depend on the conditions more than the bike and my speed would probably depend more on me than the bike. But still I'm put off actually commiting to the Trance by the feeling that there might be something even better for me (Anthem X 29er, for example). But how much better could it really be though and would the difference really have that much effect on what I could ride, or how fast, or how much fun I'd have. Probably not, but I guess we all want it make the best choice possible.

Cheers

Andy

toasty

supersonic wrote:

I disagree (position wise), for a given rider, seat angle and chainstay length, you will be in the same place in respect to the rear axle as the bottom bracket to ars* height will be the same. Just with more or less seatpost showing. However the actual weight distribution will be a little different. But the larger frame, with a higher headtube will tip your cog further back anyway, somewhat neagting that you have to reach a little further.

Picking a random bike, 70 degree seat tube, each inch you raise the seatpost, you move back towards the rear axle by 0.35 inches. My Meta for example is running a 400mm seatpost with a 67 degree seat tube angle, which leaves me far too far back along the stays. In relation to the BB it's fine, pedalling on the flat is fine, sat down the front end is very keen to take off though as I rotate around the rear axle.

High headtube will do nothing surely? Run less rise on bars, flip your stem etc. Your wheel base however is fixed. Pushing everything to silly scales, with a 5 meter wheelbase, sat in the middle you'd never lift the front, with a tiny wheelbase you'd easily pivot around either axle.

1mancity2

Your front wheel lifting probably has more todo with technique than the actual size of the bike, I ride a medium giant reign and had a medium giant trance before that (5"11) and they both felt right but it all depends on how you ride.

Friend has a large anthem and I rode that and it just felt so big and twitchy, not for me.

Only thing you can do is get a demo on a large that way at least you have tried both. good luck with the new bike when you finally get that decision sorted.

styxd

Picking a random bike, 70 degree seat tube, each inch you raise the seatpost, you move back towards the rear axle by 0.35 inches.

Ignoring other dimensions like chainstay length (which is often the same on all sizes anyway) and assuming seattube angle is the same.

It doesnt matter if its a small or large bike, the saddle height is the same, so basically you're talking nonsense.

Think about it!

toasty

styxd wrote:

Picking a random bike, 70 degree seat tube, each inch you raise the seatpost, you move back towards the rear axle by 0.35 inches.

Ignoring other dimensions like chainstay length (which is often the same on all sizes anyway) and assuming seattube angle is the same.

It doesnt matter if its a small or large bike, the saddle height is the same, so basically you're talking nonsense.

Think about it!

I'm thinking. I think that a longer wheelbase makes it harder to lift a front wheel, as I said.. I also think that on bikes with shorter wheelbase, if you run too long a seatpost you end up too far over the rear axle, making the issue worse. Smaller bikes have a shorter wheelbase.

No?

styxd

I can see what you're saying, but you dont end up any further back over the rear axle. The seat height is a constant, as is the seat tube angle. How the seat gets to its height doesnt matter (whether thats with 350mm of post extended or 50mm of post extended)

styxd

But yes, I agree, a bigger bike has a longer wheelbase and you'll probably have more weight over the front wheel. I'd always go for the larger bike as it means you can run a shorter stem. Making a small bike fit doesnt really work

toasty

Yeah, the rear axle argument was a bit bobbins I concede on that one

I think I just get scuppered by that due to being off the top end of the scale:



Worst climbing bike I've ever owned shockingly, due to being too far back. Far easier on the Pitch I had afterwards. Both XL frames, the only difference being the Pitch had a huge wheelbase, the Mojo had a tiny one.

styxd

My saddle height looks similar to that on my bikes!

I think some manufacturers increase chainstay length on larger frames (they do on road bikes anyway)

29er's are probably the way forwards if you're tall (or so Im told)

I'd like to try one but I wouldnt buy one since I cant imagine they'd be much fun for playing about on.

toasty

styxd wrote:

My saddle height looks similar to that on my bikes!

I think some manufacturers increase chainstay length on larger frames (they do on road bikes anyway)

29er's are probably the way forwards if you're tall (or so Im told)

I'd like to try one but I wouldnt buy one since I cant imagine they'd be much fun for playing about on.

Yeah, my old style Scandal 29er seems fantastic. That said, they've curved the seat tube and made the stays shorter on this years, hehe. I do wonder if keeping the stay length the same on all is just a cash saving measure sometimes. Most full sussers use the same rear triangle/swingarm between all models too.

styxd

Yeh, I guess it keeps costs down and sizing isnt really as critical on mountain bikes as it is on road bikes. I prefer shorter chainstays if anything, but I like riding stood up.

I think shorter stays feel better for climbing (they do on the road anyway)

simonp123

Just chipping in having recently test ridden a large framesize Trance X. I'm 5'11" (not the 6' I thought I used to be it turns out :shock: ) and I found the large felt too big. It felt like I sat in the bike rather than on it, and the long wheelbase made it feel very slow to turn. I found the front was still quite easy to lift though, though not unless I wanted it too. By contrast I also rode a large Anthem X and this I found near impossible to lift the front on due to the way you weight is distributed differently.
In the end it was a compromise between the large feeling too big and the medium being borderline on the small-end, but my prefernce was for manouverability and i will adjust the coackpit setup to suit.

I wonder if with this being the first full susser you have it is amking the front seem to lift too easily. When I switched I found a similar effect as when the rear squashes under pedalling it creates a rear-ward weight shift and tends to lift the front wheel. I had to alter my pedalling to be much smoother when riding full suss, but once I did that it was fine.

styxd

It felt like I sat in the bike rather than on it

And thats a negative? From what you read in magazines/on forums, most people prefer to feel sat "in" the bike rather than "on" it.

bennett_346

styxd wrote:

It felt like I sat in the bike rather than on it

And thats a negative? From what you read in magazines/on forums, most people prefer to feel sat "in" the bike rather than "on" it.

I don't. I like to be high on the bike.