So the local tire shop where my fiance recently bought some tires recommended having them “siped”, which is where they slice through the tread blocks to make more grooves that supposedly open as the tire deforms due to road contact. This allegedly helps grip and heat dissipation. They wanted to charge $40 extra for it. She opted out.
So can anyone offer any hard evidence supporting or refuting the value of siping? I can’t help but think that if it made your tires so much better, the tire manufacturers would just do it at the factory.
The only testimonials I’ve found on the internet are basically along the lines of “yeah, I got it done and it made a big difference,” which is pretty subjective and poorly measured, given that when you try it out, you’re probably buying a brand new set of tires, so will notice a difference regardless of the siping.
Shit, you want tires slashed? I’ll do it for a lot less than $40.
Sounds like a load of BS to me.
A. I doubt they would actually do anything to the tires, just take your money. Notice they said the grooves would open up later, as the tires deformed? Probably long enough for you to forget you had it done.
B. Cutting the rubber of the tire with a knife? Good way to get a flat, IMHO.
C. Would you like underbody rustproofing on that car?
D. I’ve also got a bridge for sale, if you’re interested.
As with undercar rustproofing (nod to Gabe) I gotta wonder, if it’s so freakin’ wonderful, why doesn’t the manufacturer do it?
I’d imagine (endearing naïf that I am) that the tread on the tires was carefully designed by Very Smart People using Complicated Computer Programs and Much, Much Onroad Testing such that it is already optimized in terms of traction. Durability and tire life, not so much, natch, but traction, yes?
And some bozo at the shop with a utility knife is going to improve on their design?
Most good snow tires I’ve bought have had sipes from the factory. They’re supposed to help the tread clear snow better. I’ve never seen it in an all-season or summer tire.
The most expensive, sticky, grippy tires you can buy have big, solid tread blocks meant specifically not to deform much. Siping makes the tread less resilient, which isn’t going to give you better grip charactersitics. I wouldn’t be surprised to learn that it helps a little in the rain, though. Wouldn’t bank on it, however.
Factual part of answer:
When I was into off-road racing we used to sipe the tires for the race car. We cut great big grooves in the tread with a special tool that was a large U shaped blade that cut by getting very hot and melting the rubber out of the way. No knives were used. The smell was horrible.
IMHO: Podkayne nailed it. The guy with the 'puter that designed the tire probably knows way more about it than the guy at the tire shop.
All tires are “siped”. Sipes are the smaller openings in the tread. The operation you’re referring to is most commonly performed in high-performance situations where the tires are used for a brief period of time, i.e., a road race, tailored to conditions, and the tires are quickly replaced. For a set of street tires, it’s pointless unless you just want to spend more money. Hand-siped tires will wear more quickly due to the increased deformation of the tread blocks, and heat is actually increased…which, in competition conditions, can be a plus.
In some cases, particularly dirt racing tires, it’s been common practice for years to have “secret” siping patterns for differing track conditions. But they replace these tires after very few miles/races.
On a street tire…it’s an additional $40.00 in the dealer’s pocket for a few razor slashes. Unlitimately, it depends…is this a new set of treads on your hot-shoe girlfriend’s Ferrari, or new skins for the Pinto?
Well, not to come to the defense of something that might be complete BS, but it’s not some guy cutting with a utility knife – they have a machine that does the slicing to the “proper” depth, which is no deeper than the larger grooves you’d stick a penny in to measure tread depth. Also, you can see the cuts on the finished tire, but they’re razor thin, so they don’t really open up unless you press on them. It’s not like they’re charging you for something they didn’t do.
I seriously doubt it’s actively bad for your tires, I just question how beneficial it is. It sounds pretty bogus to me, and, like I said in the OP, if it was all it was cracked up to be, why wouldn’t the tire company have designed it in?
And alas, the fiance doesn’t drive a Ferrari. They wanted to sipe her Ford Focus’ tires.
Depends what you mean by bad. Most things to do with mechanical design are a compromise between competing performance priorities. As others have said, siping may well improve some aspect of performance. The question is what “bad” things it does to other aspects of performance.
Siping does improve traction, however I have only heard of it done to off-road (mostly rock-crawling) and high-performance/racing car tires that get used on pavement. It’'s not something reasonable people pay to do for their regular tires. I don’t recall ever hearing that it acellerates tire wear appreciably, but it may void the warranty in some way.
Siping [proper] is not “cutting more grooves”, it is more like “making razor-blade slices”. After a slice is made, it’s hard to see it from a couple feet away.
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When I drove race cars and street legal tires were required, siping the tires greatly improved the traction of the tires, especially in classes where we raced on a wet track. The only problem doing on street tires is the tires will not last as long. And they tend to pickup and hang on to small rocks and pebbles so you hear the tick tick tick sound from your tires when driving at slow speeds. And of course, the sound of the rock bouncing off your wheel wells as you pick up speed.
You will notice that snow tires now have more and more siping in them. The tires I usually got siped where off road tires that I used year round. Summer and winter.
The story I’d read/heard was that siping as done by the gizmo at Discount Tire or wherever, is more a relic of an earlier age.
Apparently the old tires didn’t have such great tread designs or rubber compounds, so they cut transverse slits across the tread, making it grip better. Apparently this thought was also the genesis of the funky slit rubber tread of the old topsider shoes, making them more grabby on wet boat decks.
Nowadays, the tire engineers know all about siping, and engineer it into the tires. Bridgestone/Firestone have “keyhole” sipes, where the shape of the slit changes as the tire wears. Michelin has weird zig-zag sipes.
I suspect that arbitrarily reducing this carefully designed set of tread blocks and sipes into your own set might change some of the performance characteristics, and not necessarily for the better. Noise would likely go up, for one thing.
The off-road guys do it, but that’s mostly because on the big mud tires, there aren’t any sipes, because they’re designed for use in mud, where sipes wouldn’t help much. But when they go on rocks or pavement, they’ll help, so these guys home-brew their sipes.
