Length of spikes (especially for Aussie readers)

Most synthetic tracks in Australia allow athletes to use a maximum of 7mm (1/4") spikes in their shoes. I’m curious to know if most sprinters choose to use this maximum allowable length spike, or the shorter 5mm (3/16") spike?
Personally, I feel more comfortable using 5mm (3/16") spikes and have had less injuries wearing them, although I am unsure what the difference between the 2 spike lengths would be from a performance perspective as I have not raced in 5mm spikes before.
Could it be that heavier sprinters require longer spikes than lighter sprinters?
I’d also like to know what difference there would be using pyramid vs Christmas tree vs needle spikes? From what I understand, Christmas tree spikes are best for softer synthetic tracks like the Sylvania Waters track in Sydney and Mentone track in Melbourne. As long as an athlete doesn’t slip, could 5mm spikes actually be a better choice than 7mm spikes due to a slightly shorter ground contact time?
For the aussies reading this, what is the most commonly worn spike length on these tracks:
Albert Park, Melbourne
Santos Stadium, Adelaide
Domain Stadium, Hobart
Bankstown Stadium, Sydney
Sydney Olympic Park
Glenhuntly Athletics track, Melbourne
Sandringham Athletics track, Melbourne

34 views and no replies! I know there are quite a few aussies here. Any ideas?

Neospeed, no idea.

I know pro runners (Handicap races on Grass) use different sizes. I heard of guys using 22mm, whilst others had said they can’t run with them that big and use 15-18mm

Why not try both and see what you feel most comfortable/fast with.

The majority of shoes have 7 spikes, the IAAF Allow up to 11.
If a spike can be pushed into a car tyre then it will be gripped by the rubber in a synthetic track.
Nail spikes were originally used on cinders. Good traction, disadvantage is the rubber gripping the spike.
Needle spikes are used in starting blocks, the sharp point penetrates deep into the rubber and the rubber grips the sides stopping slipping.
There are two types of christmas tree spikes, stainless steel and anodised aluminum. The aluminum is a soft material and distorts easily.
The 5mm spikes were suggested for the blue track in Newcastle, they did not have the funds to finish the track so put a 2mm top over the shock pad made from binder and blue oxide. Anything over 5mm penetrated the top allowing water to reach the shockpad.

A christmas tree spike started as a cone spike and the parts that was held by the rubber were removed. Because it has several flat spots it is the hardest to get to penetrate the rubber and has the most recoil.

Thanks, sady.
From a performance perspective, do we want spikes that penetrate the track (needle) or spikes that compress the track (Xmas tree & pyramid)?
Regarding spike length, I had always raced on synthetic tracks in 7mm, but since switching to 5mm in training, I’ve been feeling good and think that there may be less chance of hamstring injury in shorter spikes, although I could be wrong.
Any thoughts on this topic, yelood?

I asked your question on facebook and here are the replies. Mathew is probably the answer that is best, not sure if it is right.

Alec - The thinking behind the xmas tree spikes is that they compress the track rather than puncturing it, which slightly reduces force and time required to lift the spike out of the track.

If you think about the difference between 5mm and 7mm this way: 5mm would be less likely puncture the track surface (think about pressing you finger into a balloon - the further you press, the more likely it is to pop.) Even if it did penetrate it would intuitively take less time to remove from the track.
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Alec Thomas However, without knowing enough about the bio-mechanics of sprinting, perhaps the slightly longer time push against the track is more important than time off the track.
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Joel - The more force you can put into track quickly is the key Alex
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Alec - Great, so if the athlete has the ability to transfer their maximum force to the track in the time it takes for the foot contact with 5mm spikes, then 5mm spikes would be best. If the athlete can’t deliver their maximum force in the foot contact time caused by shorter spikes, then longer spikes would be better. In saying this, athlete technique and ability are probably thousands of order more relevant in determining foot contact time than spike length.
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Mathew - Too many variables to give a definite answer. However from my limited knowledge I would say (and I’m guessing really) as long as you are not slipping, the shorter the spike (with the less surface area) the better. The more surface area of a spike the more friction it generates, which creates the stability and ability to apply most of your force into the track, however it also requires more force to both push the spike in and pull the spike out of the track (that is why large buildings use long piles on soft ground conditions and javelin throwers use 9mm in the heel) given these statements, as long as you aren’t slipping, the 5mm needle spike would be best. Having said that the amount of force we are talking about here is minute, may as well play it safe and use the 7mm as slipping would waste far more force than vertical friction. Also I don’t use spikes over 9mm with blocks as I don’t feel like I can push with long spikes, some athletes may feel the same with the 7mm.

I like you calling out the members Neospeed.
I am also guilty of not giving you or sharing with what I know.
I will tell you this.
I remember CHarlie saying you never want the spikes to be too big , meaning too long. And your point about the surface is valid but some of this comes from your own preference and your own feeling about how you feel when you run.
Sometimes longer spikes are forbidden as they tear up the tracks.
I was invited to Melrose Games in NYC when I had been running well. I was in lane one , directly near the long jump pit. The sand sprayed onto the track and I slipped and fell pretty hard. We were running on boards and my spikes had not been adjusted to the track. It’s rare these days to run on a board or wood track but it’s more normal for winter climates and portable tracks.
As for the pattern… I always put in as many spikes as was allowable.

Oh another thing I remember doing is using 2 different sizes of spikes on the pad of the shoe. Using small pin spikes ( not sure what the material of these pins was) combined with the larger length but still allowable on each shoe. Here is what I know for sure. I only ever had a few different pairs of spikes and it was not overly emphasized for my situation. This is not to say it’s not a concern or something you need to ignore but it’s one variable of a multitude of variables that go into your training. The availability of spikes is far greater today than it was when I was running.
There are some very good comments here so hopefully the information has been helpful.

Thank you and apologies for posting member’s name. I have now edited that post.

Depends on the type of grass. If the grass is soft the longer the better.

On synthetic surfaces traction makes no difference.