Gravel bike bike fit, if you see what I mean…

Is a bike fit as critical on a gravel bike as it is on a road bike?

I had a bike fit for my road bike several years ago. When I got a new road bike, I made sure the set up replicated as near as possible the original bike…

Fast forward a couple of years, and I’ve now added a gravel bike (Specialized Diverge) as an n+1.

I haven’t been through the whole bike fit process or even bothered trying to replicate my road bike set up, and it’s been comfortable so far.

However, as stock, the seatpost has layback PLUS I run the saddle as far back as possible (I have a long back and arms compared to my leg length).

I’m looking to replace the seatpost with a dropper post, but most dropper posts don’t have layback so I’d be shifted forward by about 20mm.
I’m just wondering what effect this will have and whether I’d need a longer stem to compensate…

The alternate would be to get a KS Eten-i dropper as that’s the only one I can find with layback but having some difficulty finding one locally…

Why wouldn’t it be? A gravel bike is very similar to a road bike and is ridden for long distances with a lot of time sat in same position, i.e. not much moving about, standing etc,.

The seat height and back/forward compared to bottom bracket should be the same if it works well on your fitted road bike. Moving forward or back uses the leg muscles differently and changes the hip angle but if you haven’t felt any difference on multiple hour rides then maybe it doesn’t make that much difference too you.

Yes! In particular your hand position, especially with any bags attached.
My fit was OK, then put a handlebar roll on, couldn’t move hands around much and got ulnar nerve palsy doing the badger divide, took weeks to resolve. So for me yes, but think about it differently as you move around the bike more

However, as stock, the seatpost has layback PLUS I run the saddle as far back as possible (I have a long back and arms compared to my leg length).

So why is the saddle pushed back? Long back and arms means longer stem/reach. Pushing the saddle back is really not the way to correct for that.

Who did your fit?

I had my first bike fit last week after over 20 years of regular riding and while it didn’t tell me much that I didn’t already know or suspect, I did find it very interesting and useful.

How old was the bike you had the fit on, and how long ago was that? I ask as my road bike is 14 years old, the main reason I had the fit was because I am considering a Diverge and wanted to make sure I get the right size. My bike is a 51cm frame and is a little too large for me (inline post and shorter stem to compensate) so I should really have gone 49cm all those years ago. However, geometry has changed enough over that time that I’d need a 52cm Diverge.

Turns out my MTB is also a bit large! (I also knew that deep down. Perils of buying ex-demo online during COVID and supply shortages)

IME for gravel/CX I prefer a fit that is more rearwards than forwards to get better rear wheel traction and avoid front wheel washout. Increasing stem length to compensate for reduced reach isn’t a route I’d go down.

I’ve found saddle setback and angle make a significant difference to arm and hand fatigue/comfort, especially on the gravel bike. I’ve got quite a skinny hard road saddle on my gravel bike currently (Fizik Antares) set back as far as it will go on a 20mm setback post. This seems to pedal well and takes as much weight off hands as possible as your body effectively balances over the pedals, more weight back, less weight on hands (that’s a very unscientific way of putting it).

I *think* I’m proportionally longer legged and shorter upped body, I know I seem to have run handlebars higher and closer than everyone else for a given bike size!

On the other hand, I’ve moved my road bike saddle back and forth by 20mm or so recently and it is noticeable but I don’t think it’s a deal breaker.

A bike fit is only part of the comfort equation. And it depends on what the fit was designed to benefit or eliminate.

How long ago was the bike fit? Are you as flexible or as fit and strong as you were when it was carried out?

Bike fit numbers may be set in stone for some but for me it’s just a rough guide. Trial and error and changing parts is way it works for me, albeit the expensive way.

So why is the saddle pushed back? Long back and arms means longer stem/reach. Pushing the saddle back is really not the way to correct for that.

Who did your fit?

Just to be clear, the saddle is attached to the post at the furthest point forward on its rails, so that’s what I mean by “saddle pushed back” i.e. I’ve extended the reach as much as possible.

The fit was done about 4-5 years ago, I think. I can’t remember the guys name but as it was done in Vancouver Canada, I doubt that’s relevant 😉

I’m not the most flexible person in the world but I don’t think I’m significantly worse than I was back when I had the fit…

Anyway, I’m gonna slide the saddle forward on the rails by about 20mm and go for a long ride as see how it feels…

Just to be clear…..

I believe mert means that you shouldn’t adjust the saddle position to account for reach. The saddle position is adjusted relative to your cranks to achieve happy pedalling dynamics. The reach is then set with the bar and stem.

Using the saddle to adjust reach can throw your pedalling off and add strain and or discomfort where it shouldn’t be.

Yep and when saddle back a lot you will be using different parts of your leg muscles. When you put it forward by 2cm (and raise saddle a bit) you will use the tops of your legs more, you hip angle will be lower (easier pedalling for some) but your weight will be more forward so you may feel more pressure on your arms/hands.

The saddle position is adjusted relative to your cranks to achieve happy pedalling dynamics. The reach is then set with the bar and stem.

Partly.  Do a squat to about halfway down with your arms out in front. Effectively a bike position without the bike.  As your arms go further forwards, your bum goes back to maintain the balance.
Maintaining the balance relieves stress on the body.

Remember to compare the seatpost clamp design, some are longer and reduce the amount you can move the saddle back and forth… So reducing the layback by 20mm could effectively be 15 or 25mm change in seat position.

I keep mulling over a bike fit because I also run my saddle towards the back of a layback post. My stem is 90mm and bike should be about the same size so feels like I shouldn’t need to push the seat back so much. However it’s a lot of cash when the bike is comfortable and any changes might not be noticeable.

I’d be shifted forward by about 20mm.
I’m just wondering what effect this will have and whether I’d need a longer stem to compensate…

The problem with extending the stem to compensate is that your C of G is then likely be too far fwd for comfort. You’ll transfer more weight onto your hands and the bike will be going off road.
Try reducing stem reach so that the saddle to bar reach is shorter but your C of G is in approx the same place relative to the cranks as it was before. You’ll be a bit more upright.
A gravel bike might mean mostly road-like riding or it can be a lot of tracks and old-school XC so it’s subjective, generally I think a shorter position and slightly more rearward weight bias than a road bike might have is a good thing for an average gravel bike.

Long back and arms means longer stem/reach. Pushing the saddle back is really not the way to correct for that.

To stay in balance on a bike you might do some of both, saddle setback and stem length. Get saddle position right first for balance, then sort the stem + bar from there.

Blah, blah, blah Practical(ish) suggestion;

Why don’t you move your saddle forward by 20-25mm and go for a good long ride OP?

Then you’ll know if it’s going to be terrible or not with the inline post, if it’s truly unrideable you can stop and move it back.

You can also maybe play with stem lengths, but first of all find out if the single change you’re considering is terrible or not.

You could pay a Bike fitter to do the same thing in their studio, but outdoors is already there and free and it’s sunny today (at least here) 😉

I believe mert means that you shouldn’t adjust the saddle position to account for reach. The saddle position is adjusted relative to your cranks to achieve happy pedalling dynamics. The reach is then set with the bar and stem.

Exactly

To stay in balance on a bike you might do some of both, saddle setback and stem length. Get saddle position right first for balance, then sort the stem + bar from there.

More of one than the other though, i’ll chop and change stem lengths all day to get it right, saddle set back is something that needs thinking about.

You’ll be a bit more upright.

And if you end up too upright, you might have the wrong size bike…

What Cookeaa said. Play around with a few things on your own first. But remember to adjust 1 thing at a time and try them out in isolation (the same as setting up your suspension should be done). You might save yourself the cost of a bike fit which could be spent on more fun things.

Well, I moved the saddle about 20mm forward and went for a 4hr, 1100+ m climbing/60% gravel ride yesterday and it wasn’t terrible and my back isn’t f++ked, so that’s good!

Someone up there suggested che king out the clamp of the new seatpost to check whether clamping position my make a difference – which is a good idea but neither of the seatposts I’m interested in are actually in stock so I’m going into this blind (assuming LBS get back to me to confirm they could actually get either…)

The current (stock) stem is 105mm which seems fairly long for a gravel bike and I’m not sure I’d want to increase that.

I’m intending this bike to be used for a mixture of more old Skool xc and rail trail type stuff.

Glad your saddle adjustment worked OP.

It may well be worthwhile breaking out your tape measure and putting it over all of you bikes and filling out a form like the park one below for each (there’s an MTB one too):

You don’t need to populate every field, but having all the relative positions of contact points for every bike written down acts as both a useful record and a helpful tool for comparison.

Knowing where in space the bars, saddle and BB are relative to one another and the wheel axles is far more useful than tweaking saddle fore/aft position in isolation or changing the stem based on intuitive guesses alone… if you have a comfortable setup record it now just in case.

Your original fit might be a useful guide, but every bike is different and it should probably be used as a loose starting point not a rigid goal.

Is a bike fit as critical on a gravel bike as it is on a road bike?

You’ve lot me with your first comment. Bike fit is critical on a road bike but A bike fit might not be. I have had a couple of bike fits roughly around 2003/4. Not sure I learnt much I didn’t know already. If you ride a bike a fair bit, are prepared to experiment, maybe have a photo taken or two and have read around the subject a bit then unless you are stupendously racy an actual paid bike fit is not all that.

Then gravel/cross – a bit more stack and a bit less reach for me (measured to the bar contact points rather than the centre of the top of the top tube). Achieved either with tweaking the components or the frame dimensions