Bias ply to radial air pressure conversion

[TMF]

I'm new to the forum and will properly introduce myself when I take some better pictures. The one below was day of purchase of an '88 with rusty fittings, etc. Those are long gone a couple of days later.

I've been going through the online service manual and see my '88 came from the factory with bias ply tires. Recommended pressures were 33 and 33. I'll eventually arrive at pressure settings after some experimentation but does anyone have throughts on a general rule for air pressure of modern radials compared to '88 era bia ply tires carrying the same loads?

IMG_20230429_184455770.jpg

[Captain 80s]

Welcome!! Even that day, it was a good looking Hawk.

Tire pressures really come down to personal preference as long as you are in a reasonable range. I wouldn't be in the high 20s and I wouldn't be at the listed max load rating pressure either. Play around. You'll probably find you are ending up around the mid/high 30s on that light bike, maybe into the low 40s on the rear All my bikes have slightly different settings for them to feel and perform like I want them to, but I ride everything from 50s to 1000s.

When I was racing I typically found I liked about a 10% increase from pre session to post session pressure, and adjusted my cold pressure accordingly. Lower tire pressures will (generally) run hotter and higher pressures cooler.

Running too low can contribute to cupping and running too high can give you abnormal/accelerated center tread wear (in my experience).

But again, it's mostly about how you like it for your weight, bike, tire brands and usage. The big take away is experiment a little. Just like moving around your controls or adjusting your suspension for you.

[TMF]

Thanks for the response. I always thought the 10 percent rise was to get track tires hot enough to grip and that street rubber would get greasy at those temps. It's about time I called Dunlop, my current favorite and ask for their temp rise recommendation. I'm not really concerned about traction but do like to minimize wear. I'll repost if I find anything interesting.

[Talon]

I just look for somewhere between 33-36 on street tires, bias or radial. Essentially what the manual calls for.

I don't bother with pressure increases on the street. I set them pre-ride and I'm done.

[Captain 80s]

I just look for somewhere between 33-36 on street tires, bias or radial. Essentially what the manual calls for.

I don't bother with pressure increases on the street. I set them pre-ride and I'm done.

I don't do that for the street either. I have a range I set to, and go. But I have done it on some new-to-me brand/models just to see.

[6]

It's REALLY hard to get a set of street tires hot and keep them there. Almost impossible

[Captain 80s]

It's REALLY hard to get a set of street tires hot and keep them there. Almost impossible

You must have some pretty damn boring roads around you.

[6]

You must have some pretty damn boring roads around you.

People get mad at me for saying this. So let me preface. I'm not preaching and I mean no offense to the Quick Street ridera out there. But this is what I've found.


You can't load a tire that hard, over and over and over again continuously without letting it cool on the street. Warm, ok. Hot. Id bet against it. A hot set of tires you don't want to touch with your bare hands..


On the racetrack it takes a lap and a half to two laps to get a set of tires up to temp. Depending on the track. Long enough straightaways can eve start to cool them back down.

Running race pace on the street, for three, four minutes in a row without slowing down, just doesn't happen often. And if it does at some point you're hitting the long straight away, or going to have to slow or stop... Maybe with the exception of some of these deals gap guys, and California Canyon guys and shit but, from what I hear, there's some spots out there. You can run pretty close to race speeds for a little while .. but normal aggressive Street riders don't. And if you can get them up to temp you're not keeping them there.

I ride real fast on the street. But still nothing like what it takes to get a set of tires hot on track.


That's why street tires are set up to work well when they're cool, and why race tires are a terrible choice on the street.

This is my OPINION, and my experience as a racer, and reckless Street Rider, ive run my race take offs on the street for years. This is not a scientific analysis, and I've been wrong before. I'm Not preaching. This is just a subject i've put a lot of time, testing and thought into. Race tires on the street are terrible because you can't keep heat in them.

[Captain 80s]

33 - 36

[Forcerouge]

I usually put around 40 psi (around 3 bars).
It's a bit on the hard side, but it feels great cornering, at least in my opinion. The tire deforms less, it is a lot more predictible.

Usually it's better to slightly over inflate a tire than underinflate it.