Thursday, January 07, 2010

How To - Comfort On A Bike

Today, some thoughts on "comfort".

I recently ordered a custom (all aluminum) frame from Tsunami Bikes. The builder asked me what I rode now, and if I felt comfortable with it. I told him my current bike is a SystemSix and I'm good on it for 100+ miles, 8+ hours.

The builder told me my new frame would feel extremely similar.

I thought, "How can he tell??"

Then I realized that comfort has to do with the front and rear of the frame. For the rear, my SystemSix has an aluminum rear triangle. So will my new frame. They both have beefy chainstays, slimmer seatstays. Therefore they'll feel the same.

The front end - I'll be using a familiar carbon fork (I already own it, and it's installed on an aluminum framed bike, and I've ridden it for those previously mentioned 100 mile days) and the same stem/bars as normal, so that's all the same too.

So, when you define comfort, think about what you're looking for. There are maybe three types of comfort:

1. Hands - if the bars, stem, fork, front wheel, even your bar tape are too stiff, too unforgiving, your hands hurt. If your bars are too low or too far out you'll put too much weight on them. Less comfort.

Steel bars transfer vibrations really well, aluminum or carbon not so much. Since I'll have aluminum bars, that's not a problem.

Steel stems, too, transfer a lot of vibration. Tubular steel stems, like the one I ride on the track, are nice and rigid, but given the choice, I'll take aluminum.

2. Saddle - Given similar wheelbases, if your saddle, post, rear tire are too rigid or too unforgiving, you'll have saddle discomfort. I seriously think frames have little to do with overall comfort with the saddle, again within a certain wheelbase range (+/- 1 cm). Yes, my tandem, with its 18-wheeler wheelbase, is much more comfy, and yes, my track bike, with its go-kart wheelase, is a bit less comfy.

When you hit a bump, your frame isn't the only thing to flex - it's your tire and saddle first, your wheel next, and then your frame. If you're out of the saddle and rocking a flexy bike, the frame will flex too.

The key here is the saddle and tire - get firm but forgiving ones and you'll be good, like a good mattress or couch. Too soft and it'll feel like you're riding in mud. Reducing air pressure on the road isn't really effective by itself unless you get a larger tire (else you'll flat too easily, or your tires will wash out in a hard turn).

A super rigid tire is a bear to ride too, even on an otherwise "flexy" frame. I learned this vividly a long, long time ago. I tried out a friend's bike, one that felt really flexible when I did the "push down on the pedal while standing next to the bike" thing that I like doing. I figured the bike would feel like mush, but my friend claimed the frame wasn't mushy at all.

Oddly enough, when I rode it, I felt a huge contrast in comfort (meaning how nice is it to ride) and flex (how efficient it feels). My hands and butt were going numb due to road buzz, but when I jumped the bike felt totally mushy.

Things didn't compute. If my hands and butt go numb due to road buzz, I figure that means the frame is really, really stiff. Therefore the frame ought to be really stiff and responsive.

A frame that feels mushy (I define mushy as "when I do a hard jump in a big gear, the chainrings move enough to make the chain rub the front derailleur"), it means the frame flexes a lot. That means it should be pretty pliable too.

My friend's bike had half of each characteristic. What gave?

I put my own wheels on the bike and suddenly the bike was comfortable and mushy. The discomfort didn't come from the flexy frame, it came from my friend's overly rigid tires.

3. Fit - The last comfort factor is fit. How does the bike fit you? Usually the saddle height has little to do with comfort, but with a too-high position, especially on a rough terrain bike, you can't unweight yourself as easily and therefore your "saddle" is uncomfortable.

The usual suspects are the two saddle-bar measurements, horizontal and vertical.

When I say "horizontal", I'm referring to the overall length from the saddle to the bar. If this distance gets too long you end up with a lot of weight on your hands (and therefore arms and shoulders). You may get numb or tingly hands, and road shock will seem a bit more pronounced in the bars.

"Vertical" refers to the vertical drop between the saddle and bar. Once again, too much of a drop will put a lot of weight on the bars.

Interestingly enough, having too little drop or too little reach will also cause some discomfort.

A long time ago I fit a recreational rider, a woman in her forties, someone that did some aerobics classes but was otherwise sedentary, to her bike. It was a hybrid model I'd sold her years prior. She wanted to ride but had some back discomfort. The hybrid put her in a slightly bent over position - the straight bars and high stem made for a pretty upright position.

I asked her if she'd be willing to experiment a bit, on my dime so to speak. I installed a long, flat stem, slammed it down into the fork (it was back in the quill days), and put bar ends on her straight bars. If it didn't work I'd work along more conventional routes, but I thought that weighting her arms and using her core would result in reduced stress on her back.

She ended up with a position that, if she was holding the bar ends, would almost resemble a time trial position, except she had to hold up her upper body with her arms (no arm rests).

The result?

She felt much more comfortable.

In fact, she felt much less comfortable trying to sit up just a bit. She basically leaned over until her back was comfortably stretched, and stayed in that position while she rode.

The lesson here is that the long, low position favored by pros could possibly be the position you can use too.

I wasn't thinking of that when I was on the trainer last night. I did a 20 minute test (failed miserably - 246 watts, and when I "went hard" in the last three minutes, I went down in wattage).

Afterwards, a bit disappointed, I decided to do some low rpm power bits, punish my legs a bit for being weak. I got in the drops, kept my torso low, and churned away. As my rpms dropped (I was shifting up), my wattage rose, until I was doing a steady, gear-churning 275 watts.

I crouched down, lower and lower, until my face was just above the bars. My old weight wouldn't allow me to do this - my torso would get in the way - but my new, improve "me" did.

I rode, my face a couple inches above the bars, my shoulders low, my forearms reaching up to the drops, and at a pretty significant angle (!).

Looking in the mirror, my position looked really uncomfortable. But I could breathe, I could pedal, and it didn't feel bad.

I may not ride all day in that position but, hey, maybe when I do a Commesso move (he pushes enormous gears in a super low position), I can churn a gear like he did in the 07 Giro.

I realized that I'd be able to replicate this position with a bit more practicality once the new frame arrived. The longer position would let me get lower without putting the bars directly under my nose. The shorter head tube, even with the headset installed on top of it (the differences would almost cancel each other out) would get my bars down a touch.



Anonymous said...

Awesome post as usual.

I'd like to say that the 'step on pedal frame flex' test can be deceiving.

At a local shop, I thought I had a crack in my frame (turned out to be a scratch). The mechanic stood on the pedal of my CAAD9 and put his weight on it. The entire bike 'torqued' and 'flexed' under his (light) weight.

That flex gives some comfort. The caad9 isn't a noodley bike.

I'd also like to add that BB's and cranks can add to a lot of what you feel where your feet touch the pedals.

I don't like people getting caught up in arguments of frame flex since even engineers can't quite agree on it. I.e. the stiffest frames ride like bricks and suck...

I'm excited for you to get this frame. I can't believe I'm responsible (partially) for it. The missus is more responsible since she gave the all important permission.

-YR (growing old)

Aki said...

I blame you for the frame, no one else. The missus just went along with it. Actually I've been conditioning her by mentioning Cervelo and stuff like that, $3k-$5k (thanks to things like Excel catalogs). So when I mentioned a custom frame for $650... well, I think she was wondering if that was for just the fork.

Anyway, I'm really starting to jones for this frame. I am also looking at a second "race changing" equipment change, and I'll report on that when I make the change. The second change I don't blame you for anything, it's all my fault. More expensive too. You should point out more inexpensive equipment changes I can make. Heh.