rally tire pressure?

I have a set of D Mack Grippa DMG3 175/70 14 tires for my Neon. what is a good pressure to start at?

I'd start at 28psi hot and drop from there to see if you get any extra grip out of a slightly lower pressure.

In reply to ¯\_(ツ)_/¯ :

thanks

Going rallycrossing with my old Neon?  Have fun!  Agreed that 28 psi is a good start unless you have a very rough course, then you may need to go up - I have debeaded one of those tires at an event once, but WOR/OVR events have a history of being on pretty rutted ground.

The sidewalls on those are VERY stiff, I would run them at higher pressure to keep rolling resistance down.

Where will you be running it? If you run it at a DRSCCA circle track/horse track the tires might last only one event.  I have destroyed rally tires in one day twice there, once at I96 and once at Marshall.

depends on the event. I've run as low as 20psi in muddy events and DMaks are notorious for being hard tires. I would opt for lower in those tires in any situation for better grip. 

rallycross I would keep the pressure higher depending on the location as de-bead in ruts becomes an issue. 

In reply to eastsideTim :

I am in northern Michigan at my family's cabin near the village of Comins. T he snodrift rally runs just north of here. I am driving some if the rally stages and scouting trout fishing spots. I love the car and do plan to rallycross it. Thank you for your hard work setting the car up.

Braden

28 psi is working well. I had started at 42 psi and dug trenches with the tires. They hook up like a good dirt bike tire now

In reply to pilotbraden :

That is a really cool picture!

This makes me happy.

In reply to BlueInGreen - Jon :

Thanks for a great car. If you and / or Eastside Tim ever want to come up you are invited

28 psi was working well then I had a rear then a front  go flat . both were debeaded. I guess I'll try higher pressure.

That's extremely surprising- the DMack 15s are known for having beads so stiff that they won't come off the wheel even if the entire center tread of the tire rips out.  Maybe the 14s are a looser fit?

In reply to ¯\_(ツ)_/¯ :

Smaller wheel diameter also means less total bead surface.  So even if it's just as tight, the total force required to pop the bead will be lower. 

In reply to rslifkin :

If the tire has ever been debeaded, it will come off much more easily a second time.

There are SO many factors involved, including wheel type.

Pete. (l33t FS) said:

In reply to rslifkin :

If the tire has ever been debeaded, it will come off much more easily a second time.

There are SO many factors involved, including wheel type.

Good point.  Same thing if the tire has been dis-mounted and re-mounted a couple times.  Beads never seat as tightly as they do the first time as things wear and stretch a little. 

I'm not as familiar with d-mack but I usually ran 23-24 or so psi on the micchies or Silverstones on rallies and then up to 28 on a rutted rallycross. One event in loose dry dust I got my best stage times at 20 psi but that was pushing it and I debeaded a tire which cost me the overall for that day, crossed the line with what was left of the tire flopping around the wheelwell, 2 seconds outta 1st place dammit. 

I was looking at the wheel tire combo and the wheel looks wide for the tire. 

Those tires probably want a 6" wide wheel at the absolute maximum- if they're a little bit stretched you can probably get away with it at a higher pressure, sorry for the bad initial number there.

¯\_(ツ)_/¯ said:

Those tires probably want a 6" wide wheel at the absolute maximum- if they're a little bit stretched you can probably get away with it at a higher pressure, sorry for the bad initial number there.

Assuming they are on the same wheels I had them mounted on, they are 14x6".  Also possibly relevant to this, although my memory is foggy, I think these were soft compound, but may be medium.  I want to say soft, because at the time, my thinking was they would not get a ton of miles over their lifetime since I was just rallycrossing with them.

On gravels for rallycross I usually start around 26 (on a  2800# car). If I need some last-ditch grip later in the day, I've dropped down as low as 16-17 before with no issues. For stage rally, usually upper 20s. I used Grippas for a few seasons back in the day and I recall I was usually around 25-27 on them. 

Keep in mind, these are actual gravels, not the "grasstrack" tires a lot of rallycrossers use (e.g. MaxSports, etc.) 

¯\_(ツ)_/¯ said:

Those tires probably want a 6" wide wheel at the absolute maximum- if they're a little bit stretched you can probably get away with it at a higher pressure, sorry for the bad initial number there.

This. when i ran Dmacks in that size, it was on 5.5 and 6" widths at most. I never once debeaded them, even at low pressures. And the Dmacks run narrow. The 175s are WAY more than 10mm narrower than the 185s, I can tell you that from experience. 

Thanks for all of the information. I left them at the cabin. I'm going back in a week or so and will mess around with them then. As far as I know they are on the wheels that eastsidetim used.