An international forum for people interested in modern high performance road going sidecars. Forum Index An international forum for people interested in modern high performance road going sidecars.

 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Tire pressure and load

 
Post new topic   Reply to topic    An international forum for people interested in modern high performance road going sidecars. Forum Index -> HPSidecar Technical Discussion
View previous topic :: View next topic  
Author Message
IanJ



Joined: 21 Jul 2005
Posts: 52
Location: Seattle, WA, USA

PostPosted: Thu Oct 27, 2005 7:01 pm    Post subject: Tire pressure and load Reply with quote

This has been discussed in a number of topics, but I'm hoping to clarify the situation for myself. I have an 82 Goldwing with an EML GT. The bike has 135R15 (which I think are 135/70 R 15, but they're just called 135R15) tires, and the sidecar tire is a 145R12. Others have said that they're running very low pressures, like 15-20 psi, in their 185-200 series tires, because the load rating is ridiculous overkill for the weight of the rig -- 1000 lb per tire vs. 900 lb for the whole rig.

I was running 40 psi in my little 135s (a holdover from my frugal ways with motorcycle tires, I guess), which became obviously wrong one wet evening as I tried to stop before hitting a car which pulled out in front of me -- no damage done, but I was near maximum grip, and not slowing down fast enough. After reading the various tire discussions, I lowered the bike's tires to 30 psi, and the sidecar down to 20 (from 32). Grip is better, but I have a feeling I've gone too far. However, I don't have any clue how you're supposed to tell. My ideal solution would be to find some way to look at the footprint of the tire (like a piece of plexi built into a ramp or something) as I inflate and deflate the tire, but does anyone have any tricks for this?

I finally sent email to EML today to see if they could help answer this question, but I'd also like to know what you guys think about this. The Firestone F560s I'm running claim to be rated for 780 lb at 35 psi. The rig weighs 1240 lb with me on it, according to the scale at the dump (which displays in increments of 20 lb), and about 300-350 of that is the sidecar, including the 80 lb of ballast I usually carry. If the load:pressure relationship were linear (which I'm sure it's not), I should be running 20-23 psi.

I'd appreciate any insight you guys have on this topic.
_________________
2006 Ninja 250
1982 Honda Goldwing/EML GT Hack
Back to top
View user's profile Send private message Visit poster's website
docmike



Joined: 27 Jan 2005
Posts: 630
Location: Eastern NC

PostPosted: Thu Oct 27, 2005 7:55 pm    Post subject: Reply with quote

I don't claim to be an expert on this, but the wife's R80RT / EML Tour T has the 135 x 15 on all three wheels. Not sure what the aspect ratio is but they're pretty high profile. Others I talked to recommended running 40 psi or so. The idea was that the higher profile tires are more likely to roll of the rim with lower pressure.

The old EML importer recommended the same range pressures for the K11 / EML Speed 2000, but I've been running 20 - 24 there.

I know that probably wasn't much help, but that's all I know.
_________________
Mike Currin
93 BMW K1100RS / EML Speed 2000
89 Honda GB 500 (6,700 miles, all original except tires)
67 Triumph 650 chopper
92 Suzuki GS500 (eldest son)
Back to top
View user's profile Send private message
IanJ



Joined: 21 Jul 2005
Posts: 52
Location: Seattle, WA, USA

PostPosted: Thu Oct 27, 2005 8:10 pm    Post subject: Reply with quote

That's ok, it's something. Any data is an improvement at this point. I do feel a certain level of side-to-side squishiness with 30 psi, and one of my concerns was that I wasn't keeping enough pressure to ensure the tire stayed on the rim. Maybe 35 is a better choice. I suspect I'm just going to have to experiment, since I know any advice I get here is going to be rules of thumb and approximations in any case.

We'll see what EML has to say about it, assuming they care to answer a question about a kit they sold to someone 20 years ago... Wink

What size are the tires on the K11/Speed?
_________________
2006 Ninja 250
1982 Honda Goldwing/EML GT Hack
Back to top
View user's profile Send private message Visit poster's website
RG



Joined: 31 Jan 2005
Posts: 16

PostPosted: Thu Oct 27, 2005 9:39 pm    Post subject: Reply with quote

I run 135x15 tires on my rig @ 23 psi front 25 rear. It weighs just under 590lbs wet.
The last time i checked, temps were even across the tire at these pressures.
On a ~70deg. day the tires got to ,if i remember correctly, about 100 to 110deg. after a brisk ride. Too low tire press will run hotter especially at the edges. ---RG
Back to top
View user's profile Send private message
IanJ



Joined: 21 Jul 2005
Posts: 52
Location: Seattle, WA, USA

PostPosted: Fri Oct 28, 2005 12:20 am    Post subject: Reply with quote

Your total rig, bike and sidecar and all, is just under 590 lb? That's a light rig! Mine weighs just under twice that, so it sounds like 30 psi may be a reasonable choice for me.

What kind of bike/hack do you have? I was pondering making a Ninja 250 hack, which probably would have ended up around that weight.
_________________
2006 Ninja 250
1982 Honda Goldwing/EML GT Hack
Back to top
View user's profile Send private message Visit poster's website
RG



Joined: 31 Jan 2005
Posts: 16

PostPosted: Fri Oct 28, 2005 4:11 am    Post subject: Reply with quote

IanJ,
My outfit is that aluminum BMW pictured on the forum home page a couple of weeks ago. ---RG
Back to top
View user's profile Send private message
IanJ



Joined: 21 Jul 2005
Posts: 52
Location: Seattle, WA, USA

PostPosted: Fri Oct 28, 2005 6:09 am    Post subject: Reply with quote

Ooh, cool. I love the look of that rig, it must have taken a huge amount of time to form all that aluminum. Now the whole "weighs nothing" thing makes perfect sense. Worship
_________________
2006 Ninja 250
1982 Honda Goldwing/EML GT Hack
Back to top
View user's profile Send private message Visit poster's website
Paul



Joined: 27 Jan 2005
Posts: 182
Location: Utah

PostPosted: Mon Oct 31, 2005 3:49 pm    Post subject: Tires with no aspect ratio Reply with quote

Tires that have no aspect ratio listed - like 145R12 - are usually 80 series.
Back to top
View user's profile Send private message
docmike



Joined: 27 Jan 2005
Posts: 630
Location: Eastern NC

PostPosted: Mon Oct 31, 2005 5:14 pm    Post subject: Reply with quote

Quote:
What size are the tires on the K11/Speed?


They're 175/65 x 14

total rig wieghs about 950 pounds.

Mike
_________________
Mike Currin
93 BMW K1100RS / EML Speed 2000
89 Honda GB 500 (6,700 miles, all original except tires)
67 Triumph 650 chopper
92 Suzuki GS500 (eldest son)
Back to top
View user's profile Send private message
IanJ



Joined: 21 Jul 2005
Posts: 52
Location: Seattle, WA, USA

PostPosted: Mon Oct 31, 2005 5:28 pm    Post subject: Reply with quote

I did some testing this weekend (not very formal testing, but testing nonetheless) and discovered that at 30 and 30, the rear tire gets warm (up to about 65-70 F on a 50 degree day), but the front and sidecar tires are remaining cool, just over ambient temp. I was doing emergency braking practice with small bat turns at the end of each run to get re-oriented on my drag strip (an empty commuter parking lot next to the freeway), so the rear tire was getting a lot more friction than it normally would.

Wet braking with 30 psi was possibly better than with 40, I couldn't really tell. I was still able to lock any of the wheels pretty easily. I suspect the Firestone F560s are not very good allweather tires, which is dissappointing. In dry braking, 30 psi was <i>definitely</i> better than 40. Although I didn't measure stopping distances, it was much harder to lock any of the wheels in otherwise similar conditions. I think lower pressure is a step in the right direction.

I think the next step is to lower the front and sidecar pressures a bit more to see if I can get temperatures evened out in less aggressive riding.
_________________
2006 Ninja 250
1982 Honda Goldwing/EML GT Hack
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic    An international forum for people interested in modern high performance road going sidecars. Forum Index -> HPSidecar Technical Discussion All times are GMT
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group