Cold Weather & Mountain Bike Suspension

If you’re like me you ride through the cold, damp and at times snowy months of winter, even if you don’t want to. You may have noticed during those cold months that things can begin to feel a bit… slooow. I’m not talking about trail speed either, although I’ll be the first to confess things slow down in that department as well. What I am talking about is the reaction from the bike. I haven't consistently noted the air temperature or conditions to say where I notice it, but it’s there.

Sluggish feeling suspension can result in less traction and more feedback from a harsher ride. With the ground usually soft and slippery during the cold months, this adds insult to injury. Each ride could see different damper adjustments as you chase better ride quality. Add your own slower reaction times and it’s no wonder we can feel like shit when riding in toque season.

I’ve heard comments like “do a run and things will be back to normal”, or “the cold doesn’t do enough to notice.” I don’t believe either statement and I wanted to find out what’s recommended to keep dampers working well when temperatures plummet. Some brands were unable to provide feedback they were happy with—their engineers didn’t have “enough” data on the effect of the cold. Others were pumped to dive in and offer their thoughts and feedback. From World Cup support techs to independent tuners, everyone offered thoughts on the cold and were surprisingly similar in their thoughts.

Jordi Cortes (FOX Racing Global Technician and World Cup Wizard)

Jordi is the guy we often see harassed by the world's best FOX supported downhill athletes in World Cup team videos. Wrenching on suspension and tuning for the fastest athletes is no easy feat. I wanted to get the thoughts from someone that works with a brand, but with some of the best riders and Jordi was perfect. His responses are based on years of experience rather than tech sheets.

How significantly do you believe bike suspension is affected in cold weather?

Depends on how cold really. It definitely thickens lubricants and makes things feel slow, but there’s just as much effect on the human side of it. Cold fingers and toes don’t have the same feel as warm ones.

What changes to cause these effects?

Oil viscosity for the most part.

Is it the same with all suspension brands/products?

I’ve never really looked into this, but probably not. It’s possible higher quality equipment would actually change more because of tighter tolerances, more oil, greater use of hydraulics.

There are claims that a short section of trail is enough to warm the suspension, making cold weather impacts no longer an issue. Where do you stand with this?

Well, how cold is it? But I’d say so. At least for a fork which is where you’d feel most of the difference. But again completely relative to how cold we’re talking.

What temperature do you start to see significant effects (most people could feel it)?

Hmmm I’d think at whatever point you as person starts to feel it. Maybe 50ºF (10º C) or so.

How can consumers adjust their suspension to best compensate?

Hard to say. If you feel confident making changes you can open a bit of low speed damper settings. This is probably more relevant in a DH setting rather than trail bike.

Do you believe there's a point where nothing can be done to compensate?

Absolutely.

Steven Mathews (Vorsprung Suspension Founder and Aftermarket Upgrade Provider)

Steve Mathews is the man behind Vorsprung in Whistler. He's incredibly knowledgable and always happy to discuss suspension, or bike tech in general. Steve and his team in Whistler have pushed out products that often end up becoming future releases from major suspension brands. They also perform suspension product services.

How significantly do you believe bike suspension is affected in cold weather?

Quite noticeably—mostly it feels slow, unresponsive and harsh. Seals also get harder and lose their ability to seal properly—hence you see a lot more people getting stuck-down forks in the winter than in the summer, especially on forks like the Bluto which are commonly found on fat bikes that people ride in the snow. On top of that, cold makes the human body way stiffer and less flexible (try opening/closing your hands quickly when they're really cold—they move crazy slow) and so everything hurts the hands more in particular. It also hardens the rubber in your tyres—you don't have quite as much grip at the best of times then.

What changes to cause these effects?

Cold weather increases the viscosity of the lubricants, damping oil and increases the hardness of the seals. Increased seal hardness increases drag and stiction, and when bath oil gets particularly thick it increases the viscous friction at the bushings quite substantially. Dampers also see a pretty substantial increase in low speed damping (both compression and rebound) which doesn't do bump absorption any favours.

Is it the same with all suspension brands/products?

They're all affected by the same mechanisms—to what degree is the question and I haven't quantified that thoroughly enough to differentiate much between different products in that way (although the differences between forks vs shocks is noticeable for sure). Coil sprung stuff is definitely less affected than air sprung stuff though, since there are no seals there to increase drag.

There are claims that a short section of trail is enough to warm the suspension, making cold weather impacts no longer an issue. Where do you stand with this?

It depends on the product, the oils used and how severe the cold is really. If you're riding at say 0ºC and you have an air sprung rear shock that's generating quite a bit of heat and has an air can somewhat insulating it, it can definitely begin to open up and behave fairly normally within just a few seconds on a descent. It'll also cool down quite fast too though - if you stop for even 10 seconds the temperature will drop substantially, because aluminium is a great heat conductor and disperses heat very efficiently. Forks, however, have a really huge surface area and they're fully exposed to the wind/air too—you can warm up the damper a bit for sure, but fork dampers don't generate that much heat anyway, and the lower legs, stanchions and all the seals contacting them (wipers and air seals) as well as the bath oil will all stay cold.

What temperature do you start to see significant effects (most people could feel it)?

Around or perhaps just above freezing (0ºC) seems to be where it becomes strongly noticeable to pretty well anyone. Between 5ºC and 40ºC there's not much noticeable difference in my opinion, but below 0ºC is definitely noticeable.

How can consumers adjust their suspension to best compensate?

Adjust for faster rebound speed, reduce (soften) low speed compression damping, make SUPER sure your tyres aren't at a higher pressure than is necessary, and use thinner oils (eg 5wt or 10wt instead of 20wt in the lowers) during the colder months. Warm gloves will help keep your hands warm and reduce the sensation of harshness that way too.

Do you believe there's a point where nothing can be done to compensate?

I think so—if for example you're riding at temperatures far below -10ºC your suspension wasn't ever really built to operate "well" in those temperatures. It might move up and down a bit but it certainly won't perform well, and air spring seals in particular are prone to leakage at those temperatures. I can't even offer solutions to those wanting to ride at those temperatures simply because we don't frequently see those temperatures in Whistler so we've never adequately tested specific cold weather seals or low temperature oils. There's precious little information out there about suspension oil behaviour and viscosity at particularly low temperatures too—most viscosity data is given at 40ºC and 100ºC but extrapolating far beyond those bounds is not necessarily valid. So all you really have to go on is the pour point which isn't even published for a lot of suspension oils.

Bryson Martin (DVO Suspension Founder and CFO. MTB Suspension industry Veteran)

Bryson needs no introduction. He's been involved in suspension for a lot of his adult life. He's developed heaps of knowledge in that time and has used it to produce excellent suspension products that achieve their ride characteristics in a different manner than the rest of the major manufacturers.

Bryson provided tech from research they’ve conducted at DVO rather than answer the specific questions.

Bryson: Here's some data I pulled up on some of the suspension fluid we are using:

1. Viscosity Index for 7wt oil: at 40 degrees Celsius it’s 24.6 V.I. and at 100 degrees Celsius it's 7.1 V.I. So you can see a large difference in the viscosity index when the temperature drops from 100 to 40. I don’t have viscosity numbers for temps below 40 Celsius but I can tell you based on experience that a fork feels much harsher in temps around 0–5 degrees Celsius. The greater the viscosity index of the fluid you’re using, the greater latitude in temperature changes but it's generally meant for higher temps. Here in California, summer temps are 40+ Celsius and if your bike is basking in the sun with those black stanchion tubes, internal temps can be much higher than 40.
2. Our seals and o-rings are made from NBR (nitrile butyl rubber) along with some other fancy additives and can operate in temps as low as minus 30 degrees Celsius. But I’m sure these low temps make the rubber stiffer and generate more stiction than they do at warmer temps. Cold metal parts moving against cold rubber o-rings and seals will feel sticky and harsh. Last year while testing in Sedona we set our forks next to the propane heater before each ride so they didn’t feel like cold honey was trying to flow through a couple of piston holes.
3. If you’re going to ride in colder temps (sorry if people do that) and you still want plush feeling suspension I suggest going with the lightest suspension fluid you can get away with based on the manufacturers recommendations. Located in California, we don’t normally ride in cold temps but rather 40+ Celsius temps.

Dougal Hiscock (Engineer at Shockcraft in New Zealand)

Dougal is someone I first stumbled across while researching some unrelated suspension topics. He makes some very strong points and is very knowledgable. He's also happy to talk shop and share his learnings. Coincidentally, Steve Mathews of Vorsprung also mentioned him and recommended I get in touch, noting that he was well versed on this topic.

How significantly do you believe bike suspension is affected in cold weather?

It all depends what you mean by cold and what you're expecting. Many don't ride much below freezing (0ºC) and others will ride down to -15ºC or so. For me, all my lab testing stops at 0ºC and I don't ride below about -5ºC unless it's for cold testing. Even then I noticed huge differences from 20ºC in both lab and riding tests.

What changes to cause these effects?

We have damper oil thickening up in the cold, bath oil thickening up in the cold, and we have seals and plastics contracting and hardening. Greases can also turn very hard.

Thermal contraction of different materials change tolerances and clearances of parts, it also adds more friction and damping to the seals. In deeper cold conditions we can have oils becoming so thick that the seals cannot hold them back. Causing temporary oil leaks.

Is it the same with all suspension brands/products?

No it's not. The brands and types of oils used by different companies vary enormously in cold conditions. The seal compounds are also all different and have different shrinkage and hardening as they get colder.

Some big brands feel slow and dead at 0ºC. Others have a difference so small that people just don't notice.

There are claims that a short section of trail is enough to warm the suspension, making cold weather impacts no longer an issue. Where do you stand with this?

That all depends on how cold it is and how much energy you are putting into the suspension. But it would never be true to say it is no longer an issue.

In cool conditions—on downhill trails—a fork or shock will warm up the fork damper a few degrees, warm up the rear shock a bit more, and that will help. But we have a lot of air cooling and the sliding parts of a fork (lowers, stanchions and crown) are an excellent heat-sink to outside. Keeping the sliding parts all near ambient air temperature except in extreme use.

Downhill shuttle runs at +5ºC is going to feel close to normal. Trail riding at -5ºC won't unless your suspension is very well prepped for the cold.

What temperature do you start to see significant effects (most people could feel it)?

At 0ºC (freezing point) people who do feel changes in their suspension will realize their suspension is less active and noticeably slower. Kind of dead feeling and transmitting bumps through instead of absorbing them. Unless the suspension has been very well prepped for the cold. In which case it could feel completely normal.

How can consumers adjust their suspension to best compensate?

Using the best fluids is the starting point and works for forks and rear shocks. Using the best fork wipers is second and obviously only works for forks. Also using only greases which work well in the cold instead of heavy oil in shock air-cans.

The worst damper fluids I have measured (from relatively big name suppliers) thickened up 10x between 40ºC (a standard temp for measuring oil viscosity) and 0ºC. Standard fluids used in production forks and shocks thickens up around 7x. Quality mineral fluids like Motorex around 5–6x. The best damper fluid I have found thickens up only 2.6x from 40ºC to 0ºC. That's a huge range and impacts ride quality enormously in the cold if you use the wrong fluid.

It's worth noting that synthetic fluids are not guaranteed better in our temperature ranges and the published figures of pour point doesn't always translate to how good it is between 0–40ºC. The best damper fluid we sell (Shockcraft Hot Oil Pink) is a mineral fluid.

Bath oil variation is enormous and after years of testing and trialling I'm still testing, cataloging and trialling. We use Supergliss 100K for most applications and it's amazing at being slippery. But at 0ºC it is 16x thicker and you can feel it really slowing things down. Below -5ºC it can push past wiper seals. We have thinner Supergliss variations which I haven't yet finished testing, fully synthetic 5W40 (35% thinner at 0ºC) for people who run hot and cold and a 0W40 (60% thinner at 0ºC) for those who are happy to swap fluids for winter.

For wiper seals, Manitou found a new material for their Mastodon and Mattoc wipers that reduced all the low temperature stiction to the point you just can't tell. They use those to -15ºC and in my riding at -5 they work as well as a normal fork at 20ºC. It was a game changer for my winter riding when they were introduced.

SKF aftermarket wipers are great for everything else as a low friction wiper that is still reliable and long lasting. In the cold the already thick bath oils thicken up to the point that weaker wiper seals just cannot peel the oil film off the stanchions. So it just slides right past and your fork appears to leak. But stops again when it gets warm.

Do you believe there's a point where nothing can be done to compensate?

Manitou have achieved full functionality at -15ºC in their Mastodon fork and that work crosses over to their Mattoc line and I'd expect new releases. But they live and work in snow-shoe type country where some people need that. Most recreational riders call it quits at more like -5ºC.

Ultimately I don't see a problem making suspension that would still work in temperatures where humans won't. We have the experience of other industries (like snowmobile) that cross over pretty well and fluids that will do the job. But is there any point? In those temps human powered transport moves very slowly and the need for excellent suspension response is reduced.