New MG Red SH2 for 2024

The new SK2 and SH2 tire is proving to be an odd duck. We have found it to be more sensitive to track temperature changes than the old SK and SH. Overall the contact patch offers more grip than the old SK and SH compounds and the sidewall is much softer just like everyone expected. However, the tire seems prone to overworking that results in your best laps very very early. We have seen it come in early, fall off around lap 4, and then come back in at lap 8-12. I think the new tires overall operate best at 1-2 psi higher than the old compound, but there are outlier situations.
We have run as low as 8-9 this spring, but not sure it was the right call. We also ran as high as 18 on a warm sunny track (mid 80s air temps). The 18psi is a track that typically likes more pressure, but I didn’t expect to need that much with the new tires on a warm day to be able to generate grip. Picked up 1.5 seconds going from 10-12 up to 17-18 on 2 race old tires, so it was clearly the right direction.
I think the big difference is the soft sidewall. If you have corners with high loading they seem to need more pressure to keep the sidewall from rolling too much and negatively affecting grip.

Its all voodoo…

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Thanks! It sounds like going up close to where you were (~18 psi) might be a good idea at Fremont since it’s all very high loading twisty-turny. We’ll see how it goes!

Fully depends on track surface. Because the sidewall is softer, you need more air on slippery tracks to generate surface temp in the tire, because the tire is absorbing more force than a hard sidewall would. The “spring rate” is therefore softer. On a grippy track, you’ll run less air because you need the tire to stay in the temperature window better with the increased friction.

I played around from 12-20 this past weekend at New Castle and settled in the 12 range. Much more and the tire would overheat. When I snuck a peek at some of the top guys air gauges, they were all around 13 psi hot. Much lower and the sidewall would start to fold. I know guys were running much lower in earlier races on totally different track surfaces. On both the 3F and 9F wheels I was seeing best laps at 4-5 consistently in every session.

It’s not terribly complicated, it’s just less fool-proof than the old tires were because with the soft sidewall you can actually make the tire work in different ways.

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Just an FYI that that 14.5 PSI recommendation youre looking at on MG’s site is a hot tire pressure. That would mean somewhere around a 12.5-13 PSI “starting” pressure.

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My recommendation, make a 5-8 lap practice run and get the tires warm. Then work on adjusting hot pressures until you find what you like. Once you do, let it cool and document cold pressures. It will give you a good starting pressure for cold tires.

General rules still apply:
need more grip => needs more pressure
need less grip => needs less pressure

But with the softer sidewall you may occasionally find situations where you have to color outside the lines to make it work. That’s what we found practicing and racing the previous weekends at the track I was discussing earlier. Just too much sidewall flex. Track regulars said go up, we did, and it worked better.

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I think I might be the outlier here, but I REALLY like the SH2 so far. I run an older Eagle in 206 Masters at NCMP usually. All I did was widen the overall front and rear about an inch and bolted them on.

Since the switch I have closed my gap on the pointy end of the field as compared to last year a decent amount. I much prefer how the kart handles now, I think the softer sidewall reminds me of a less extreme version of the really old Bridgestones I learned to drive on. To me the SH1 was numb feeling, with the SH2 I can feel that outside rear talk back to me a little before it lets go if I throw it in too hard.

I haven’t corded a set yet, but so far they seem to hold up pretty well. I ran the SIRA street race at Anderson a few weeks ago and started the weekend on a set that had 3 practice days and 1 race program at NCMP on them. We got a ton of track time and my times were always right there, so I left them on for the feature. It was in the mid-upper 80’s and I started the race at 16.5 PSI cold. Kart ran great the whole race, had a good result and the only real time drop off was from my old ass falling out of the chair towards the end.

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My son has shared similar feedback on difference in feel.

I really liked the tire too. Felt nice to have something that didn’t feel like a rock out there, and was easier to mount too.

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I like it too. I really haven’t played with tire pressure that much though. It seems to be working find for me starting where I did with the SH1 - in the 10-13psi range depending on temps and track.

Finally did some testing yesterday with my son. I came away feeling no better. @tjkoyen was there as well, and I shared my data with him. We were going in opposite direction with pressure, and both getting faster, lol.

After our fastest session, we then hit a timing wall and lost half a second. I looked at the rear tires and the wear marks were completely gone! I guess 3 race weekends and 1 practice day is the MAX for the tires.

On another note, we finally have video to review as I put on a smarty cam and ditched the GoPro! What do you know…video of every session with data overlay and I never had to touch the camera.

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I did the same, ditched the GoPro and now use the Smartycam. Video data reliability went from 30% to 100% with 1000% less effort Although, the quality is not as good it’s good enough. Also pertinent data is automatically overlayed on the video.

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I never bought one in the past due to cost, but I have probably spent more in GoPro cameras and mounts than I would have just buying the smarty cam in the first place.

I agree with the video quality, but I’m not making a movie. I want to see my driver’s hands, feet, and the track in front of him.

The data overlay is just cool, and not having to even think about it all day is a major bonus!

The only down side was it took a lot of time on the internet figuring out how to set it up. Surprisingly small amount of helpful content out there.

Yeah the auto on once the kart starts rolling is a really nice feature. Just wish they had a worthwhile camera for us content creator addicts. The cam is a 1080 job which is way too low res for today. Perfect for laptop review trackside though!

But it still bugs me that they hobble the camera.

Generally, I believe that temperature is the gold standard when it comes to tire performance. A tire’s characteristics will deviate significantly from its optimal temperature range, it may behave unpredictably and fail to function properly. Based on my experience, three primary factors influence this behavior: the type of rim, the load placed on the outer tires (which is affected by the vehicle’s center of gravity, width, and F&R weight distribution), and the pressure within the tires.

To achieve optimal performance, it’s essential to identify the ideal temperature range for the tire and then make adjustments to the other variables to maintain this condition. When you think about it as temperature instead of pressure I think mostly you will see better results.

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Great analysis Ron. This is why multiple different pressures can work in different situations. Different track grip levels will generate more or less tire temp.

With the softer sidewall, there more options on how you work the tire now and what pressure you can run to build and control temp.

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Ohh, I did forget the obvious… Track temperature and air temperature are also major factors if not the biggest factor.

Ron are you regularly measuring tire temp with a pyrometer? Or doing some testing with it and correlating that to pressures? You getting recommended temp ranges from somewhere?

MG gives a general range for all their slick tires of 176°-203°, though I’m not sure how accurate that is or how updated that info is. I have used a pyrometer sparingly, but I have one.

I am finding this too. These new tires are way more sensitive to small changes than the old tire. Where I am kind of lost is how to change pressure to account for the temp changes and by how much. Does anyone have insight on this?

I’m not sure you were asking the question this simply, but generally the higher track temp and air temp, the lower the starting pressure in the tire.

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