Do all bikes behave the same on bumps?

[timto]

When riding across expansion cracks, of which there are many on our roads, my wife's cannondale exhibits a large difference between the first 'bump' that comes through her bars and the 'BUMP' that comes through the saddle. She often gets out of the saddle when riding over bumps. My ibis is quite good - what comes through the back is larger than the front but not terribly so. One bike is alu - one is steel.

Do you all experience the same 'bump', 'BUMP' sensation?

If so I'd like to know if you have experience that indicates if changes in materials (adding/going carbon) or design (DKS, Terraplanes, ST) actually achieve a reduction in the size of the 'BUMP' that is passed up to the rider.

Any chance any ones bike has less shock through the seat then through the bars?

I realize there are many variables but I'm looking for a casual observation, of force transmitted front vs rear across bikes you may have tried. My belief is that we often set our different bikes up in a similar fashion. It would be interesting to see what frame type people have felt or perceive to have offered the most comfort

Thanks for your input

Tim

[M_A_Martin]

Over the same bumps:

My Aluminum EV2 with a carbon fork: Bump BUMP
My CSi (steel, F1 carbon fork): bump Bump
My Kirk terraplane (steel with a steel fork): mm mmm
its gotta be a big bump to make the terraplane bump, let alone Bump, and its never BUMPed...

You asked for a casual observation...

[timto]

OH yeah - that is exactly the kind of feedback I was hoping to get! Thank you - so the terraplane is that good!? ONe more Q - does performance take a back seat to comfort though? LIke when you really pull on the bars and take off?

Thanks again.

[M_A_Martin]

Hmmm...I don't think I can answer that question clearly...as I'm not much of a sprinter...Bump bump is much easier :)

Neither the Kirk or the CSi have that Aluminum-Direct-Drive feel of the EV2. However both are much more comfortable on centuries than the aluminum.

Mileage comparison:
EV2: Wouldn't do more than 60 miles voluntarily.
CSi: Century comfortable.
Kirk w/terrplane: Was ready to ride more after my recent 105 mile ride..but I was riding outside my conditioning, so 105 was it.

I have to say that I think I might be faster overall on the Kirk as the bike fits me better.


You might want to go ask your question on the Bike Fan Club.
http://www.bikefanclub.com/forum/postlist.php/Cat/0/Board/kirk

[Dekonick]

Why dont you just 'hop' em? I just make sure I have enough speed and give a gentle 'tug' with my arms n feet... voila- clear of the joints. (only if they are big or have a significant height difference... otherwise I just go over em. And - just to add a little more... my Hors is more of a Bump mmmm...the second 'bump' is really barely there.

[Ken Robb]

all else being equal a bike with longer chainstays will be smoother, especially over the second bump of the back wheel. Think about the last ride you had in a short wheelbase car; a Jeep Wrangler is a perfect example. If you sit in the front seat the bumps are about equal and not too bad. If you sit in the back seat, more-or-less over the rear axle, the second BUMP is tough. If you can't see the Jeep simile try holding a ruler horizontal and pretending you are sitting at the middle number. Now raise either end like it hit a bump. The middle doesn'tmove nearly as much as the end, right? Now pretend you are sitting over the 11" mark and "hit" a bump at 12" mark. Ge you get almost the full effect of the bump right up your spine. I've got bikes with 40cm to 45.5cm chainstays and I can tell the difference in the way they react to bumps easily.

[dbrk]

tires, tires, tires. These make so much more of a difference than anything short of moving suspension that there is, well, no comparison with respect to materials or even in terms of design (longer chainstays, etc.). Put on some nice Dugast or Roly-Poly/Ruffy-Tuffy tires and you will feel a whole'lot less bump, no doubt about that. That said, the DKS Legend does indeed move in the rear but less to take out the shock then it does to _grab_ the road on something slippery. That at least is my experience.

dbrk

[vaxn8r]

I agree with everyone else. I think frame material has almost zero to do with shock absorbtion, or lack of, with big bumps. If you didn't get that Bump! I'd have serious questions abotu frame integrity. It's about wheelbase and tires. Consider the experience on a tandem, when the captain hit s the bumps the frame soaks them up. The stoker, OTOH sits on the rear wheel and feels the brunt. Likewise, put some wider tires or lower your tire pressure, both make a huge difference in bump perception.

Now, for the little bumps, chip seal type roads, I agree, different frame materials may give you a different feel, but still not as much as frame geometry and tire size, pressure.

[jl123]

DRBK,

I still would bet that on your Moots with YBB, even if you put a tire on it such as a IRC Passella 35c, that the suspension would be provoked at times to use its travel. Have you ever tried such a wide tire on your Moots, might be a cool experiment?
Take care, JL

[M_A_Martin]

The question was for a casual comparison. No doubt, the EV2 chainstays are shorter tha either the CSI or the Kirk, with the CSi and the Kirk being a bit more similar. Tires were taken out of the equation because I was considering all three with Continental Gator Skins 23s, at 110psi. My tire and pressure of choice for ages.

The Kirk also grabs the road as Douglas mentions. I think the Mmmm factor is merely a side effect of any rear suspension.

[dbrk]

I routinely swap out the cross tires (Ritcheys) for the larger Vittoria Randonneurs on the Moots YBB. You sure do feel the rear suspension dig in when you put stress on it (no matter which tires) but on the other bikes without suspension I would attribute the cool bump factor far more to the tires (and pressure) rather than to the frame materal. Hmmm. If the DKS could take a tire more than a 28c we'd have an experiment of fair comparison too but the F2 fork limits tire clearances, of course. Designing bikes around plug-in carbon forks is a certain pet peeve of mine but what do I know? If the forks were steel we might be able to design a _whole_ bike (rather than one around the fork). So it goes.

dbrk

[jl123]

DBRK,

Did you mean you wanted to compare your DKS with the Moots or with something else?
I recently read about the technical trials that Jan Heine and http://www.adventurecorps.com/ttt/index.html are putting on next year. Indeed it would seem that many of these 'experiments' that we are talking about will eventually be part of their program. According to Jan, the French had started to think about suspension for their Technical Trials, but never got there. I see no reason Americans cannot initiate such innovation as road suspension design. I think a good name for this riding could be 'softroad'. Also since you cannot get wide enough tires on your DKS, when you get around to getting a Kirk Terraplane, which I think winds up with a similar amount of travel- especially if you get Kirk to make one thats extra curvy, then you'll be able to make some more experiements with the wider tires. I too will try to do so, when I start making some money! thanks, JL

[Andreu]

19 mm vs 23 mm. I used 19mm once ...never again they don´t do bumps.

[Smiley]

When I switched from an Steel tandem to an Aluminum one the only way I could live with riding Aluminum was to up-grade from 26 mm wide to 28 mm wide tires to absorb some of the BUMP sensations from making the switch to a stiffer frame . Thats my 2 cents as a proud Hors Categorie owner who says what bumps .

[jerk]

good tires make a huge difference...tire pressure makes a gigantic difference...chainstay length makes some difference...set back makes some difference....bottom bracket drop even makes some difference....frame design makes some difference too....it all adds up....but the right tires for the course is more important than choosing the right frame for the course. (see frame choices at paris-roubaix. everyone is using special tires, some people are using special frames.....no one is using special saddles, seat posts or weirdo dks pivots, terraplane, pivoted rear ends etc. etc.

jerk