Effect of saddle to bar drop on geometry

[SlackMan]

I'm hoping to get some helpful opinions on the following question: Suppose that one has a frame built that assumes a 5cm optimal saddle-to-bar drop, but later realizes that 0cm drop is actually needed. Also suppose that the 0cm drop can be accomplished with just spacers and a stem change. Will the geometry that was designed for 5cm drop be far from optimal at 0cm drop in the way it rides and handles? Said another way, if one can get either a 5cm drop or a 0cm drop using spacers and stem change, does the rest of the geometry also depend critically on the drop? In case it seems like a weird question, there is a not-fully-healed back injury underlying it.

[rice rocket]

It does. It changes your weight distribution, and how your front end steers since it has less weight on it. How much of a difference? Who knows, try it and tell us.

[SlackMan]

It does. It changes your weight distribution, and how your front end steers since it has less weight on it. How much of a difference? Who knows, try it and tell us.

I'd love to try it, but the question is about a frame that I would have built if I knew the answer to the question. I wonder if anyone has had to substantially raise or lower their handlebar height and can weigh in how much of a difference it made -- that would be great.

[Louis]

If this is a bike that you currently have, just do whatever it takes to get the contact points in positions that allow you + your back to ride comfortably.

Healing is way more important than going or looking fast. The handling may be affected in a way that you might notice, or you might not notice. And if you do notice, it may not be a big deal at all.

Just ride the bike.

Once you're all healed up you can then decide what to do with the bar and saddle positions.

Edit: OK, I now see you post above. If this is about a hypothetical bike, talk to the builder and see what s/he says.

[Scott Shire]

1) talk to your FB! Let him or her know your concerns.

2) I MUST recommend getting your back in order before you do a custom build. Don't pay that kind of money for a faster backwards machine that will be a tough re-sell when your form returns. Stretching is free and yoga is a nominal cost.

[SlackMan]

1) talk to your FB! Let him or her know your concerns.


Good idea. I was hoping to get many opinions, though, to see if there is a consensus.

[palincss]

It does. It changes your weight distribution, and how your front end steers since it has less weight on it. How much of a difference? Who knows, try it and tell us.

5 cm difference -- easy for anyone here to try, no tools required. Go ride in the drops or on the bar ends, then move up to the bar tops. That's about 5 cm difference. Do you notice a handling change?

Now if you happen to have a couple of scales and a helper to hold the bike up and read the scales handy, you could also try putting the bike on the scales and see if there's any change in weight distribution when you move from drops or bar ends to bar tops.

[zennmotion]

put your bike in a trainer, rest the front wheel on a bathroom scale set at a height to level the bike, and weigh the front end in both positions using an adjustable stem. This will give you some idea of how the center of gravity shifts back as the bars are raised. How useful this "data" is another question however- just another measure in the mix.

[zennmotion]

5 cm difference -- easy for anyone here to try, no tools required. Go ride in the drops or on the bar ends, then move up to the bar tops. That's about 5 cm difference. Do you notice a handling change?

Now if you happen to have a couple of scales and a helper to hold the bike up and read the scales handy, you could also try putting the bike on the scales and see if there's any change in weight distribution when you move from drops or bar ends to bar tops.

Jinx. But you only need one scale with a trainer.

[tv_vt]

[QUOTE=palincss;1447801]5 cm difference -- easy for anyone here to try, no tools required. Go ride in the drops or on the bar ends, then move up to the bar tops. That's about 5 cm difference. [UNQUOTE]

Actually, I think that's more like a 12-14cm drop for most road bars. Check the specs on most bars and they're in the 128mm - 144mm range for the distance from tops to drops.

[David Kirk]

It's a near impossible question to answer as to how much the handling might change with a 5 cm higher bar. It will change some.....how much and how much will it bother/please you is unknowable.

Now if the question is how would a builder change the basic design between two riders that were identical aside from one desiring bars that are 5 cm higher this is a bit easier to respond to..........not that much frankly.

I might change the head angle and rake just a tad to get the front center to be a bit shorter to put a bit more eight on the front wheel and one could even go as far as making the c-stays a bit longer to put more weight on the front wheel but the changes themselves would be very small.

5 cm is a big difference and this can be tough to accommodate with stem and spacers and not end up with a silly design so I would want to be sure I know where my back is at before committing to a design one way or the other......certainly as a builder if my client says I need the bike to ride just right with a 5 cm range of bar heights I wouldn't take that on.......it would need to be a narrower window for me.

But all builders are different and there is no 'one right way' despite what some builders would say. The only builders that say 'there is only one way' most often only know enough to do it that 'one way'.

My 3 cents (inflation).

dave

[RedRider]

1- Don't do anything until your back is fully healed.
2- Then go to an experienced fitter to determine your "new" riding position. Don't assume that once your back heals you will be able to ride in the same position. I don't know the extent of your injury but you might not have the same flexibility you had before or you might even have more.

Good luck and speedy recovery

[ultraman6970]

No idea what bike are we talking about but generally pretty much in any descent geometry stock bike when the stem is too high the handling is like cr@p, seen those guys that can't keep the bike aligned while riding?

As rice rocket mentioned, the handling might change but at the same time depends a lot of the rider, some riders can't handle even their own temper. No idea what bike are we talking about neither of your level of confidence riding the bike but so far I can tell, the 1st thing you might notice is that the handling might get erratic because now the weight was shifted to the back, good bikes are designed to have the weight distribution (the center of mass) between a range, if off, the front will get erratic if the rider cycling style is not like super good aswell. If you can barely ride no hands how you have the bike right now with the new position probably you wont be able to do it, test of fire.

What's the issue you want to solve? your neck hurts or something? 5 cm of drop isn't a lot either you know.

[SlackMan]

...
5 cm is a big difference and this can be tough to accommodate with stem and spacers and not end up with a silly design so I would want to be sure I know where my back is at before committing to a design one way or the other......certainly as a builder if my client says I need the bike to ride just right with a 5 cm range of bar heights I wouldn't take that on.......it would need to be a narrower window for me....

dave

Well, that settles that. That is precisely what I was anticipating doing--having a frame built that would ride just right with a 5cm range of bar heights. But if Dave Kirk says "bad idea," then that settles that. I guess I need to just keep fighting that urge to jump into a custom frame until I sort out my back issues.

Thanks all for the replies.

[happycampyer]

Dave Kirk, RedRider and others are spot-on. My advice would be to buy a used bike that has the appropriate geometry for your current position. Once you've recovered, you can probably sell the temporary, used bike without taking much of a hit, if any. And as RedRider points out, your post-recovery fit may not be what you now think it is going to be, so it's not wise to have a bike built based on what you think/hope your fit will be.

[ultraman6970]

Super good advices here, the problem is that the OP is trying to address a back problem shifting more weight to the back, he needs to shift weight off his back, just the opposite... lower the stem.

A lot of things going on if the stem is way up there.

[SlackMan]

Super good advices here, the problem is that the OP is trying to address a back problem shifting more weight to the back, he needs to shift weight off his back, just the opposite... lower the stem.

A lot of things going on if the stem is way up there.

Thanks for your thoughts! I think that my situation might be different, but I would appreciate your thoughts about it. I fractured T3 - T5 vertebrae in a biking accident. Those are situated up between my shoulder blades. Although I am well along in healing, I noticed after a 45 mile road ride this past weekend that I was sore and achey exactly in the area of the fractures (riding at about 4.5cm bar drop). I was assuming it’s a combination of having to hold up my upper body, and that part of my back probably also helps hold my head and neck up. It seems like going lower would just exacerbate the strain on that part of my back. Any thoughts?

[OtayBW]

Thanks for your thoughts! I think that my situation might be different, but I would appreciate your thoughts about it. I fractured T3 - T5 vertebrae in a biking accident. Those are situated up between my shoulder blades. Although I am well along in healing, I noticed after a 45 mile road ride this past weekend that I was sore and achey exactly in the area of the fractures (riding at about 4.5cm bar drop). I was assuming it’s a combination of having to hold up my upper body, and that part of my back probably also helps hold my head and neck up. It seems like going lower would just exacerbate the strain on that part of my back. Any thoughts?

Yes - why not just raise the stem up ~3-4 cm and go out and ride again. Keep testing and dialing it in till something works. Or maybe spend a little coin and go get a fit on a size cycle kind of thing.

[carpediemracing]

Thanks for your thoughts! I think that my situation might be different, but I would appreciate your thoughts about it. I fractured T3 - T5 vertebrae in a biking accident. Those are situated up between my shoulder blades. Although I am well along in healing, I noticed after a 45 mile road ride this past weekend that I was sore and achey exactly in the area of the fractures (riding at about 4.5cm bar drop). I was assuming it’s a combination of having to hold up my upper body, and that part of my back probably also helps hold my head and neck up. It seems like going lower would just exacerbate the strain on that part of my back. Any thoughts?

Depending on if you can deal with trainer rides I'd do rides on the trainer. I'd have a stack of spacers next to me, maybe even a couple stems, and I'd switch them around, riding them for 1-3 hours at a time (it would take me 3 hours to do 45 miles so I'd test for a 3 hour long ride).

I found that I'd have a decent idea of what to expect within a few minutes of fitting something. For me my current search was to find a good position in terms of saddle->drops. Prior to that it was determining reach. For that I used plastic totes placed next to the bike on the trainer, resting my hands on the tote instead of the bar, moving my hands to "try" different positions.

The trainer is nice because it's generally a seated thing, it has no distractions, and you control a lot of variables.

[SlackMan]

Yes - why not just raise the stem up ~3-4 cm and go out and ride again. Keep testing and dialing it in till something works. Or maybe spend a little coin and go get a fit on a size cycle kind of thing.

I was assuming that getting a fit wouldn't tell that much because the back pain is only going to start after I've ridden for >2 hours. I've never had a fit and don't know what all fit specialists know, but could they recommend anything useful in the typical time of a fitting? If so, I'm more than happy to spend the coin. I'll need a new fork to raise the stem, so I guess that's looking like money I will just have to spend to experiment.

[T.J.]

Slackman~ I went thru what you are going thru. Crack some verbs in my neck in a crash in a crit. Ended up going from 12 cm of drop to 8 and all is well now. I would suggest maybe getting one of those adjustable stems , figure out what works. Might be a cheap way to figure out what you need before making a expensive investment

[David Kirk]

Does your current ride allow for you to make large adjustments in fit with stem and spacer changes?

dave

[ergott]

Good idea. I was hoping to get many opinions, though, to see if there is a consensus.

There is only one opinion that matters here, the builder. If you trust him then it's a win. If you don't think the builder is up to accomodating you, then cancel the transaction and work with someone you feel comfortable with.

I've read/seen too many stories about too many other getting involved and mucking things up. This is between you and the builder you trust working with.

All the best of luck with it and I hope you get what you what.

[SlackMan]

Does your current ride allow for you to make large adjustments in fit with stem and spacer changes?

dave

If I get a new fork with a taller steerer tube, I can then make large adjustments in spacers and stem. With current fork, +17d stem, and max spacers, I am at a 4.5cm drop. To experiment, I'll need a head tube extender (which I have), a new fork, and then spacers and stems. Although I hate to spend money on stop-gap measures, that is looking like it might be the optimal strategy.

p.s. the reason for the limitations above is that I need a 56cm TT and yet ride at saddle height of 79.5cm (long legs and short torso). Any "normal" frame has a head tube that is way too short.

[ergott]

Maybe an inexpensive steel fork on your existing bike will allow you to get the fit you are looking for to see if it works. The investment is small in comparison to a new bike. It doesn't have to be a high end carbon fork just to see if it works. It it doesn't you should be able to flip it online since you don't plan on cutting much of the steerer.

Talk to someone local that can evaluate the best fit for you and your injury. It can't be done by us over the internet.

[shovelhd]

I'm in the camp that says wait for a custom until you are healed. Focus on stretching and comfort with your current fit. If you trashed your back and get discomfort after a few hours, that sounds pretty normal to me, even with a perfect fit.

[palincss]

put your bike in a trainer, rest the front wheel on a bathroom scale set at a height to level the bike, and weigh the front end in both positions using an adjustable stem. This will give you some idea of how the center of gravity shifts back as the bars are raised. How useful this "data" is another question however- just another measure in the mix.


What it will measure, directly, is the weight distribution. The very same weight distribution that it is alleged that will cause noticeable handling changes when it is changed.