Bike Fit: relative measurements

[grellboy]

Got quite a nice set up on my winter bike and now about to dig out my best bike. Want to make my best bike fit like my other one but frames are quite different - one has a straight top tube, the other quite curved - so comparative measurements pretty tricky. I'm now working on the basis that if I set seat height on best bike from BB to saddle to match winter bike, then if I measure the drop from saddle to bars and replicate that measurement on best bike fit should be the same (taking reach into consideration too!) Does this make sense?

 

[ColinJ]

It is going to be close, isn't it, but maybe not identical? If you have different bars and saddles on the 2 bikes then that could make a difference.

I have shallow drops on one bike and deep drops on another. I have the position on the hoods and tops pretty much the same, but the reach down to the deep drops is too far.

I have identical saddles on all of my bikes now. Ideally, I would have identical bars too but I can't afford to replace the non-optimal ones.

 

[si_c]

BB to saddle top (effective leg length) and saddle tip to centre of stem clamp (reach) are how I measure mine.

I checked the other day for the first time on two bikes and they are within 5mm of each other despite being very different frame types (steel Peugeot and modern alu adventure road). Both set up by feel rather than having a bike fit.

I wouldn't worry too much about saddle to bar drop as the frame geometry can make these quite different.

 

[bpsmith]

Whilst decent advice, if you measure comparing saddle position with stem clamp, then you could have a reasonably different position, in relation to the bottom bracket, between the two bikes.

Personally, I like to get the saddle position right with respect to the bottom bracket as my first job. Then I consider the position of the stem and bars.

Best way is to position the bike with the rear wheel up against a wall and then make all measurements from wall or floor. It’s always easier when using a solid surface to measure from.

 

[bpsmith]

Some people on here dislike the GCN boys, but this video might be of use too:


View: https://youtu.be/psbu9OH69sI

 

[Salty seadog]

I'm one for keeping it simple, straight leg with a heel on the pedal for saddle height for a starting point will get you close and make small adjustments from there if needed. As above listen to your body.

 

[derrick]

I have more than one bike, quite a few in fact, and I'm not 'average' in that I'm not very tall with long legs relative to my height. With a new bike I always set the saddle height for comfort, then ride the thing for a while. Other adjustments will become obvious as you ride the bike. I once got the chance of a cheap shared bike-fit session and took my tourer - the guy didn't change anything (except the levelling of the saddle, which was so uncomfortable I put it back how it was), so even at a reduced price it was a complete waste of money. Only you can know what is comfortable for you. I think trying to set the bike up like your other ones using measurements alone is a bit of a waste of time, because as others have said they are all slightly different in subtle ways.

Don't normally agree with a lot of what you say, but you nailed that.

 

[Paul_Smith SRCC]

I agree with what the others, keep it simple, saddle height and seatback from the BB and reach and drop to the bars-shifters.

If the saddles are the same length just drop a plumb line from the nose of the saddle, there is often a crank bolt on the LH crank that you can use as a reference point, with the crank in the same position as my drawing simply measure to where the plumb line meets.

Bar height from floor and shifter tip from saddle, if the bars are both similar with the lever positioning the same on both bikes that will advise reach and bar height.

 

[GuyBoden]

For what it's worth, once I got a comfy setup (in the1980's), I've used a Triangulation method to setup my bikes.
(I wrote these dimensions down in a notebook, these change slightly with age, mainly to a higher handle bar position.)

Centre of BB to Back of saddle.
Back of Saddle to the top of Break levers. (or where you mostly put your hands)
top of Break levers to BB.

 

[Sharky]

Loads of good advice before me.

Just to add, I always measure from pedals to top of saddle, rather than from the BB. Not all my cranks are the same length.
Also when riding on tops, it's usually a good indicator (for me) if the front axle is obscured by the handlebars.

 

[Lozz360]

I agree with what the others, keep it simple, saddle height and seatback from the BB and reach and drop to the bars-shifters.

If the saddles are the same length just drop a plumb line from the nose of the saddle, there is often a crank bolt on the LH crank that you can use as a reference point, with the crank in the same position as my drawing simply measure to where the plumb line meets.

Bar height from floor and shifter tip from saddle, if the bars are both similar with the lever positioning the same on both bikes that will advise reach and bar height.
View attachment 403471

Height from the handle bar to the saddle is a better measurement than floor to bars. This is because the height of the BB can vary quite a bit between road bikes, therefore the saddle height relative to the ground will vary for the same fit.

 

[Paul_Smith SRCC]

Height from the handle bar to the saddle is a better measurement than floor to bars. This is because the height of the BB can vary quite a bit between road bikes, therefore the saddle height relative to the ground will vary for the same fit.

Agreed, I have stated 'floor to bars' simply as it's an easy measurement to take accurately, saddle drop is actually what you do need, it's just more tricky to measure. If both bikes are known with listed data for each that will often include bb height which will help with comparisons.

When customers visit it's often after we have exchanged emails including size data of both rider and or bike, to be thorough we often check those measurements, it may not be a complete surprise how on many occasion they differ; often by quite some margin. It's not unusual that the largest discrepancies are of the rider, for example "I'm 6ft", you will be amazed how many times I have to recheck that for them when the first taken measurement is under 5ft 11"