Go Back   Harley Davidson Forums > Harley Davidson Motorcycles > Sportster Models
Sign in using an external account
Register Forgot Password?
Search


Sportster Models 883, 883 Custom, 1200 Custom, 883L, 1200L, 1200S, 1200 Roadster, XR1200, and the Nightster.
Sponsored by: Rush Racing Products

Reply
 
 
 
P
 
Thread Tools Search this Thread
  #1  
Old 04-13-2012, 06:39 AM
JimA's Avatar
JimA JimA is offline
One Of The Regulars
Join Date: Aug 2011
Location: Northern Arizona
Posts: 173
Default Tire Air Pressure?

The manual calls for 36 psi on the rear tire... How much air can I let out of the rear tire without long term damage or performance loss? I'm looking for a softer ride in the rear. I have my low rider shocks maxed, so no adjustment there...
__________________
Jim
1995 XLH 1200 Sportster

Reply With Quote
  #2  
Old 04-13-2012, 07:36 AM
grbrown's Avatar
grbrown grbrown is offline
Club Member
Join Date: Jun 2007
Location: Bedford UK
Posts: 23,624
Default

How much can you let out? None IMHO! By doing that you are likely to introduce handling and stability problems. If you are uncomfortable you need better shocks!
__________________
'Sir' Graham 5Ps, #1 Gent! Dude?
Harley owner since 1974, Founder & Life HOG Member.
1990 Officially 'Hyacinth' Blue FLHS/2008 S&S V107T, 2007 Buttercup XB12R, 2011 Merlot XL883L, MG ZT V8 281cid.
Reply With Quote
  #3  
Old 04-13-2012, 08:30 AM
IBGary IBGary is offline
Road Captain
Join Date: Apr 2010
Location: Colorado
Posts: 557
Default

+1 grbrown
Reply With Quote
  #4  
Old 04-13-2012, 09:01 AM
Mich's Avatar
Mich Mich is offline
Road Master
Join Date: Aug 2011
Location: victoria bc
Posts: 858
Default

Don't mess with your air pressure!
__________________
2012 Iron
DIY N R H S 1250, SEPST
SE Buckshot heatshields and slipons
SE round stage 1 AC
Scythe Mirrors
Black Diamond grips and foot pegs
Reply With Quote
  #5  
Old 04-13-2012, 09:14 AM
WVHogRider's Avatar
WVHogRider WVHogRider is offline
Elite HDF Member
Join Date: Nov 2006
Location: Wheeling, WV
Posts: 4,508
Default

If you go down on air pressure you don't gain much rear end softness, and you actually prematurely wear out your tire & lose some handling due to excessive sidewall flexing. In the old days, some people would lower their tire pressure due to hard tailing the bike so the ride wasn't so bone jarring. Too low of air pressure makes the rear end feel all squirrelly. Been there, done that when I found I was down some psi due to a screw in the tire.
__________________
http://www.hdforums.com/forum/image.php?type=sigpic&userid=20830&dateline=121812  6494
Reply With Quote
  #6  
Old 04-13-2012, 10:12 AM
mrfikser mrfikser is offline
Outstanding HDF Member
Join Date: Oct 2009
Location: Maryland near DC
Posts: 2,011
Default

i have found that below 30psi on my bike the rear gets loose ...and I am a light 155...if you weigh more you need to make the pressure higher....
Reply With Quote
  #7  
Old 04-13-2012, 11:14 AM
schwingding's Avatar
schwingding schwingding is offline
Road Master
Join Date: Jul 2010
Posts: 1,051
Default

Despite ALL of the advice above, I can assure you (and will put money on it) that you will see performance GAINS from your tires by lowering the pressure. Motorcycle tires are not automobile tires, they need to get hot and soft in order to perform properly. Additionally, they will deform around and in road imperfections, rather than transmitting those incidents onto the responsibility of the shocks, keeping the bike steadier and allowing you to drive it harder. You will find a softer, smoother, better handling ride as a result. Yes, tire wear will be a little more severe. Tires are made to wear out.

36 psi is your manufacturer's recommendation for a fully loaded tire - unless you have a 200 pound passenger with loaded saddle bags, you don't have a fully loaded tire.

Drop the PSI to 30 (cold), ride it. Report back - I'm willing to bet money that you will be pleased. You will probably be even happier at 26-28 (cold).

My sporty rides best at 28 front, 26 rear, cold. I'm 140lbs. My VROD runs best at 22psi cold on that big 240mm rear.

Don't want to take my word on it, fine go to a motorcycle racing forum and ask around about street tire pressures.
Reply With Quote
  #8  
Old 04-13-2012, 11:17 AM
mcw999 mcw999 is offline
One Of The Regulars
Join Date: Apr 2012
Location: Virginia
Posts: 159
Default

Messing with tire pressure is a bad idea. Try replacement springs and shocks instead. Keep tire pressure to specs.
Reply With Quote
  #9  
Old 04-13-2012, 11:23 AM
schwingding's Avatar
schwingding schwingding is offline
Road Master
Join Date: Jul 2010
Posts: 1,051
Default

Quote:
Originally Posted by mcw999 View Post
Messing with tire pressure is a bad idea. Try replacement springs and shocks instead. Keep tire pressure to specs.
Please explain how this is a bad idea.

I would make the argument that it is a better, faster, cheaper, and perhaps smarter idea to establish your preferred tire pressures than it is to change springs or shocks. It is very interesting to me how every piece of our bikes are considered fair territory to most tinkerers for performance changes, but tires seem off limits. Tires changes can offer THE single most dramatic performance change on your bike, if done properly. The pressure recommendations from HD and the tire manufacturers are set to be safe for the vast majority of riding conditions, including a fully loaded down bike. No way in hell the same psi for a fully loaded bike is optimal for a lightweight guy on a chopped up bobber, but most riders seem to think the number on the sidewall is the way to go without even considering why.

If you've ever raced anything with big tires, you'd know this. But for car pressures, we usually wind up going higher than the rec - even 50+ psi on tires with 30psi recs, but cars are not motorcycles. Motorcycles need LOWER pressures to perform properly, but very few of recreational users know this.

I was having a lot of trouble with my Sporty and I talked to a professional motorycle racer friend of mine, he laughed at me, told me to drop them down to 25, and go from there. Incredible performance gain! Same thing when I got my vrod, much better performance at lower pressures.

Now - given that it takes only a moment to alter your tire pressures, and great perf changes are possible, how much sense does it make to do something so complicated and difficult to change as shocks and springs without even attempting to see what different tire pressures can do for you?

Just makes no sense to me. Something so easy to do, but we'd rather buy expensive springs and shocks and mess with an ounce or two of shock oil. I really suspect that most shock and spring changes stay put just because it's so complicated and costly to reverse, and you don't have to think about it - there they are - advertised, with instructions, if someone said it's so, it must be.

Lower your tire pressures. You can always change it back, but you won't want to. You can even do this with your child's bicycle pump, don't even need a quarter for the gas station pump.

One final thought - think about this - your tire pressures are always changing, as much as 10 pounds per sq inch even during a single riding session. Plus, they're always leaking air. How many of us check our tires to find they're "5 pounds down" or more - was it unsafe? You didn't even notice, but you probably thought you were just becoming a better rider.

Last edited by schwingding; 04-13-2012 at 11:37 AM..
Reply With Quote
  #10  
Old 04-13-2012, 11:41 AM
grbrown's Avatar
grbrown grbrown is offline
Club Member
Join Date: Jun 2007
Location: Bedford UK
Posts: 23,624
Cool

Quote:
Originally Posted by schwingding View Post
Please explain how this is a bad idea. Thank you.
Essentially because what you said before ain't right! The purpose of a tyre is to provide some cushioning between wheel and road, but also to provide dependable grip and stability. The recommended pressures are a guide to providing those, although I will agree they are only that. Reducing pressures to significantly lower levels reduces the stability of the tyre and hence the bike, which is likely to become unpredictable and frankly unsafe. Not for me thanks!

The place to improve ride quality is with better quality tyres, better shocks and more comfortable seat, in that order. You should try a set of Ohlins shocks and experience just how magic they are to ride on! With the correct pressures of course!
__________________
'Sir' Graham 5Ps, #1 Gent! Dude?
Harley owner since 1974, Founder & Life HOG Member.
1990 Officially 'Hyacinth' Blue FLHS/2008 S&S V107T, 2007 Buttercup XB12R, 2011 Merlot XL883L, MG ZT V8 281cid.
Reply With Quote
Old 04-13-2012, 11:41 AM
 
 
 
P
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
Tube air valves subwayjoe General Topics/Tech Tips 0 10-25-2013 03:35 PM
Front tire troubles jazzy jack General Harley Davidson Chat 43 11-22-2012 08:29 AM
Ride On tire sealant James Larson Tri Glide & Freewheeler Models 7 09-14-2012 06:49 PM
Rear Air Shock Pump as a tire pump? TxCowboy Touring Models 5 09-08-2010 07:13 AM
Nail in rear tire jbmss Touring Models 15 04-20-2009 10:32 AM


Tags
1990, air, back, davidson, harely, harley, hd, northern, nrhs, preasure, pressure, sporster, sportster, tire, va


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Forum Jump

Join HDForums

Advertising
Featured Sponsors
Vendor Directory
Sponsors

All times are GMT -5. The time now is 01:46 PM.


Internet Brands, Inc.