hard front tire = pogo back tire - K-Bikes.com - Excellence in Motion
 
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post #1 of 7 (permalink) Old Oct 13th, 2010, 10:52 am Thread Starter
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Location: Newark, DE, USA
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hard front tire = pogo back tire

FYI

Just got Ocelot, 1990 K75C, back on the road after ten years parked. Naturally, I replaced both tires, which were way way too dried up to get a good grip. The local Cyclegear mounted a pair of Bridgestones. Paid the state extortion last Thursday, so I have been riding Ocelot less than a week. Just long enough to come up with a name for her.

So I start riding her, and I immediately thought her rear shock was shot. At any considerable bump I would shoot up off the seat six inches and the rear end would bounce like a pogo stick and whack me in the ass three times. Yesterday, in fact, I was shopping the internet for a new rear shock. Good thing I didn't pull the trigger.

When I got home from work last night, I checked tire pressure in front because I thought the front felt awfully hard. The shop had put 40 psi in that tire! I aired her out to 26, or whatever was in the manual don't quote me. The rear was about 40 too. I aired it out to 38.

This morning on the way to the office, all pogo was gone!

That was easy.

So on a K75C, what do you guys usually run?

Dial in info: I weigh 215. Ocelot's role is a city commute and I also intend to also ride longer freeway errands when they come up. I live in Dull-Aware, which is a sand bar between two rivers, so twisties are not a consideration. Bridgestone S-11 Spitfire tires.

Unmitigated risk aversion is the new Puritanism, complete with witch hunts, funny outfits, and solemn preachers thundering doom. The name of God is changed to Safety; the name of Satan is changed to Lawyer; but the object remains the same: to suck all the life out of life and make you live on the husk.

Last edited by Ocelot; Oct 13th, 2010 at 2:59 pm.
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post #2 of 7 (permalink) Old Oct 13th, 2010, 2:25 pm
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with crossply tyres, run 32fr and 36 rear.
Ray
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post #3 of 7 (permalink) Old Oct 13th, 2010, 2:47 pm
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if they're, BT45 Bridgestone say 36/40 for your bike.
At 215lb solo I'd say treat that as your minimum, 38/42 wouldn't hurt.

Be careful that you're not running below pressure to try and mask suspension problems, you'd be asking the tyres to work too hard in terms of sidewall flex, the contact patch will be compromised, ditto water displacement, and you'll risk accelerated wear and/or reduced grip.

after 10 years laid up, old tyres aren't the end of your recomissioning. All the fluids need doing - and fork oil would be on that list. Bike handling rule No.1: problems at the back, check the front.

good luck.
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post #4 of 7 (permalink) Old Oct 14th, 2010, 2:20 pm
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Tire pressures in the manual are for 20+ year old tire technology.

I put new Spitfires on a K75 earlier this year and 33ish in the front and 38-39ish in the rear worked quite well.
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post #5 of 7 (permalink) Old Jun 5th, 2011, 10:49 am
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Assuming 2011 bias ply tires, what is different about current technology tires that requires higher pressures? Different compounds?

I had a set of tires installed yesterday on my K75S, the shop set them at 40 front, and 42 or so rear. I had them reduce the pressures to what's printed in the book, though they were skeptical. They told me 26 might be ok around town, but the the tire would scallop.

Then new tires are Avon AM26 Roadriders, fwiw.

TIA
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post #6 of 7 (permalink) Old Jun 6th, 2011, 2:16 am
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I find 40/42 works for me with bias ply tyres (I weigh 210 pounds with gear on) on a K100RT (a bit of extra fairing weight).

When I changed my fork oil the first time an ooze of grunge came out, about half the volume it should have been too.

Pogoing back sounds like a shock issue to me. Is it the original shock? How many miles does the bike have on it? I've heard they go around 40K miles. Mine certainly needed replacing when I got the bike with 57K miles on it.
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post #7 of 7 (permalink) Old Jun 11th, 2011, 3:34 pm
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So have you got it replaced. well once the tires you have changed then check it should be working.

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