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Old 07-02-10, 02:48 AM   #1
Seijun
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Taking the sting out of bumps with a rigid fork?

I got my Kona Smoke today! First bike since I was a kid. I decided on a rigid fork because I don't want to hassle with any parts I can live without. One less thing to worry about breaking.
However, what are some things I can do to smooth out my ride without suspension? Hitting even little cracks in the pavement was very jarring. I don't know what psi the tires were at, but they are as hard as rocks. LBS was the one who filled them up, told me they should be between 65 and 75psi. I figure they are the experts, but I wonder if the tire pressure should be lowered any, from what it is now. OR maybe I've just gone soft from not riding in so many years. My tush still hurts and I was only on the bike for an hour today! It hurt less on my second riding attempt, but only because I went numb after 30 seconds.

Oh, the tires are 700c x 47.

Other than that, it's great

Last edited by Seijun; 07-02-10 at 03:03 AM.
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Old 07-02-10, 06:27 AM   #2
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Originally Posted by Seijun View Post
... I don't know what psi the tires were at, but they are as hard as rocks. LBS was the one who filled them up, told me they should be between 65 and 75psi. I figure they are the experts, but I wonder if the tire pressure should be lowered any, from what it is now. OR maybe I've just gone soft from not riding in so many years. My tush still hurts and I was only on the bike for an hour today! It hurt less on my second riding attempt, but only because I went numb after 30 seconds.

Oh, the tires are 700c x 47.

Other than that, it's great
OUCH! 'Experts'! The answer to your question is in your post: your tires are waaaay overinflated and consequently (as you say) 'hard as rocks.' I don't know why bike shops do this -- I suppose because they and/or so many customers think that higher pressure means faster etc.

Anyway: 47c tires should (depending on your weight) probably be set somewhere around 45 to 50 psi at the rear, and around 10 psi lower at the front (e.g. 37front/47 rear). Assuming you're around 180 to 200 lbs, try 40front/50 rear, and see how it feels! You should notice a world of difference and, yes, your bike will probably actually roll slightly easier on the road!
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Old 07-02-10, 06:39 AM   #3
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Just make sure you check the minimum and maximum pressures, which is on the sidewall of the tires. Your pressure "should " setttle in that range.

However, I run my 85 PSI(max) pressure tires at 92#, because that's where I like 'em the best. I weigh 190#, and I find that my Schwalbe Marathon Supremes roll the best at this pressure (700X35 & 700X40.) I don't find the ride bad at this pressure - honestly.

If you ride on very smooth surfaces, and not prone to pinch flatting, you might get away with less than the minimum. If you start getting pinch flats, you will have to bump the pressure upwards, and, additional flexing of the sidewalls is going to make them start cracking sooner (we're talking years, here).

Last edited by Wanderer; 07-02-10 at 06:46 AM.
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Old 07-02-10, 09:21 AM   #4
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Since the Kona Smoke is a bike-shop bike, you probably got fitted for the right frame size so fit shouldn't be an issue for your tush pain. Everyone has a slightly different butt, which means the stock seat that came on a bike won't be comfortable for everyone. Ask your LBS and see if they would let you try out different saddles.

Also, remember that your legs are part of the suspension system. If you see a bump coming, you should put most of your weight on the pedals and not rest all your weight solely on the seat. Your legs are designed to absorb shocks FAR better than your butt.

I would NOT lower tire pressures to significantly less than the minimum recommended pressure printed on the tire side wall-- If you run underinflated tires, you are liable to get pinch flats.

You only mentioned tush pain, but just in case you are feeling discomfort in your hands and wrists from feeling the bumps transmitted through the rigid fork, you should consider gel-padded gloves and bar ends too.
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Old 07-02-10, 11:10 AM   #5
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Ok, according to the tires themselves, the max psi is 58. I looked all over the tires and could not find a min. I probably weigh 130-140ish (no scale handy).
I think tomorrow I will go the another LBS for a second opinion on the tires, and maybe get a better fitting. There is another place in town that seemed very knowledgeable about bikes and I would have bought from them originally if they had had the bike I wanted.

My arms did hurt also during the ride but once I got off I was fine. It was mostly pain from keeping my body propped up--I am a bit out of shape.

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Old 07-02-10, 11:53 AM   #6
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Continental City Contact 37-622 700 x 37C black Reflex, 600# wt capacity, 58PSI min, 85PSI max.

there ya go - From Kona's & Conti's websites.

Sooooooo, bleed 'em down to 60#, and see what they are like - then adjust from there....

OOps, picked the wrong line ---

47-622 700 x 47C black Reflex 740#, 45MIN, 58MAX ,

soooooo bleed 'em down to 50, and go from there......

Last edited by Wanderer; 07-02-10 at 11:57 AM.
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Old 07-02-10, 11:59 AM   #7
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p.s. That's a lot of bike, for the money.......
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Old 07-02-10, 12:02 PM   #8
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It would help if you tell us the name and the model of the tires (Ok, I see someone else has done this for you, is he correct about what you have?). The tire manufacturer's web site may have a range of recommended pressures. You can inflate tires according to the recommendations of Frank Berto who measured tire flattening or drop with various tire loads. If you inflate your tires to have 15% change in height from no load to the load you, your bike, and any gear you carry present it you supposedly optimize the trade off between comfort and rolling resistance. Above this pressure you have little decrease in resistance but a significant decrease in comfort. Or so the theory goes. I have been using it myself this year and I think it is a good way to operate. It gives a nice improvement in shock absorbing and no noticeable loss of speed. Probably with careful measurement using scientific instruments I don't own and can't afford you could measure a slight loss of speed.

The Berto pressure versus load curve varies with tire width, you say yours are 47 mm so I generated a curve for that width, attached below. As someone else said you don't want to go far, if any, below the tire maker's recommended minimum pressure or you risk pinch flats so if the Berto chart puts you in that region start at the minimum the maker suggests and move down from there cautiously and only if the tire is still too stiff for your comfort. The curve is based on the load on each tire, not the total weight of the bike, you, and your gear. As a rule of thumb a touring bike with front panniers will run 45% of the total weight on the front wheel and 55% of the total on the rear wheel. A racing bike carrying no load, typically, is about 40% front, 60% rear. And a typical commuter bike with a load only on a rear rack is about 35% front, 65% rear. So you can see that the front tire should run at least a little less than the rear.

I'd not worry too much about the saddle right now. Maybe I am unusually tolerant but every saddle I have ever ridden has caused me distress at first. After a few weeks it goes away, for me anyway, and never returns. It's worth toughing it out for a while in my opinion.

Ken
Attached Images
File Type: jpg BertoPressure47m .jpg (53.6 KB, 15 views)

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Old 07-02-10, 12:28 PM   #9
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i dont see a problem with suspension forks. the suntour nrx on my kaitai works quite well. i can tighten the suspension pretty tight and it only has 63mm of travel to boot. plus hydraulic lockout on the fly. it is a joy on badly potholed and bumpy urban roads i will say.
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Old 07-02-10, 02:19 PM   #10
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I would get suspension if I was getting a very expensive bike. But for my budget, I feel much more comfortable with rigid (I would rather spend $400 on a rigid bike than spend the same amount on a suspension bike with worse quality parts overall).
As a kid I rode a rigid fork dept. store bike all over gravel roads and somehow survived, and with a hard rubber stock saddle too. If I could do that, I should be able to make this bike work for me.

@ khutch: yes, those are the tires I have (thanks Wanderer). Ok, so according to the chart...
If I am estimating that the bike will carry 160lbs total with me + groceries, that's 64 in front and 96 back. This comes out to: roughly 21psi in front and 28psi in back?? That seems really low. Do I also need to add in the weight of the frame?

Forgive my ignorance, but I have heard of this Berto pressure thing. Where is the best place to find more information?
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Old 07-02-10, 02:27 PM   #11
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I would start with the manufacturers minimum pressure, and see how it does. I don't like to go too much below the minimum, or too much above the maximum.

In this case, 45# would be worth a try. I don't think I would try to go below 40, or above 65. That's a pretty narrow window, but that's a big fat tire.
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Old 07-02-10, 02:35 PM   #12
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Suspension Seat Post.

Did it come with a suspension seat post ? If not, you might try one, pretty cheap fix and will
not add much weight to the bike. Also it may take several weeks before your butt gets
used to riding again, I would not rush right out and buy another one. After not biking for
awhile, it took me a few weeks to get used to the seat again. Now I can ride for hours.
Everyone already touched on tire pressure, so I leave that alone. Richard

Last edited by xoxoxoxoLive; 07-02-10 at 02:39 PM. Reason: spelling
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Old 07-02-10, 02:40 PM   #13
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Suspension Seat Post.

Did it come with a suspension seat post ? If not, you might try one, pretty cheap fix and will
not add much weight to the bike. Also it may take several weeks before your butt gets
used to riding again, I would not rush right out and but another one. After not biking for
awhile, it took me a few weeks to get used to the seat again. Now I can ride for hours.
Everyone already touched on tire pressure, so I leave that alone. Richard
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Old 07-02-10, 03:16 PM   #14
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No, it doesn't have a suspension seat post, but I will def. keep your suggestion in mind if I'm still hurting after a month or two and if I have any spare cash. I am in no rush to upgrade anything at the moment.

Last edited by Seijun; 07-02-10 at 03:37 PM.
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Old 07-02-10, 06:15 PM   #15
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@OP: so, which is it -- 47c or 37c? If the latter is correct, then for a 170lb load (thanks, Sheldon Brown) simply try 60 rear/50 front -- could even go slightly lower given your weight if riding the bike unloaded. I've used SB's suggested pressures for years/never had a problem, and never found an advantage in going above or below. Just sayin'; it's easy to over-think this stuff.
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Old 07-02-10, 06:44 PM   #16
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Keep your elbows bent and your weight on the pedals, not the saddle when riding over rough spots.
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Old 07-02-10, 07:03 PM   #17
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@badger: The tires are 47c, as stated in the original post.

Also, is the seat on the smoke designed more for a male?

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Old 07-02-10, 08:09 PM   #18
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[QUOTE=Seijun;11054088]@badger: The tires are 47c, as stated in the original post.

Also, is the seat on the smoke designed more for a male?[/QUOTE

Hey there -- then I stand by my original post on this! Seriously, you can't go far wrong with (the late) Sheldon Brown's recommendations on most things bicycle (I'm hopeless with link-thingies; just google e.g. 'Sheldon Brown tire pressure'.

The saddle - hmmm - assuming then you're female, yes it (the saddle) probably is 'male' on a stock non-woman-specific bike. Some women don't notice, but if you do notice some discomfort, you might need a saddle designed for a woman; typically, slightly wider in the back better to support (again, typically) slightly wider-spaced sit bones. And, make sure it's level (front to back), then adjust only slightly nose-up or down if at all, whatever works!
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Old 07-02-10, 08:21 PM   #19
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Keep your elbows bent and your weight on the pedals, not the saddle when riding over rough spots.
Good Advice ! My friend..
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Old 07-02-10, 08:49 PM   #20
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Good Advice ! My friend..
Yeah, now that I've been properly tenderized I'm learning that REAL quick.

I lowered the psi as suggested, and it did help to take the edge of things.
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Old 07-02-10, 08:53 PM   #21
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The saddle - hmmm - assuming then you're female, yes it (the saddle) probably is 'male' on a stock non-woman-specific bike. Some women don't notice, but if you do notice some discomfort, you might need a saddle designed for a woman; typically, slightly wider in the back better to support (again, typically) slightly wider-spaced sit bones. And, make sure it's level (front to back), then adjust only slightly nose-up or down if at all, whatever works!
My sit bones rest on the outer edges of the seat (about 1/2" in, or so it feels)
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Old 07-03-10, 02:51 AM   #22
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And, make sure it's level (front to back), then adjust only slightly nose-up or down if at all, whatever works!
agreed. tilting the saddle down a little bit may help. there is a nice article about this subject:

http://www.sheldonbrown.com/saddles.html#adjustment

also for me moving the saddle position back a few inch and pedalling in a high cadence helped overcoming anterior knee pain.
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Old 07-03-10, 08:12 AM   #23
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And, don't be afraid to experiment with different tire pressures. As you get more used to riding, you may find that you like different pressures - firmer will usually enhance handling and speed, while softer will usually enhance ride plushness and grip on softer surfaces. Try different pressures, even usung different pressures in different tires (fron,back) changing them by about 5# either way, until you find what's best for you. It will finally come to a point, where one or two pounds of pressure will make a significant difference.

As your body gets used to what you are asking it to do, so will your needs and wants.

The bike will also need different pressures, as you change the load it is carrying, or, your style of riding.
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Old 07-03-10, 11:34 AM   #24
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We're considering playing with the tire pressures on our new bikes, both have front suspension, but they're almost fresh from the bike shop with solid tires that send every single bump up through the seat post, on roads it's not too bad, but we've been riding on a few tow paths that are nice and bumpy. Nice sore derrieres, as me and my Lady are just getting into riding again.
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