Is a powered car tire inflator suitable for road bike tire inflation?

Question

I'm switching to road cycling. My diminutive and portable pump will likely be a pain to get 120psi. Rather than get a foot pump with either a built-in or an external pressure gauge, I'm thinking of simply getting a pump for car tires that doubles as bike tire pump.

Despite the brand of the model I'm considering, it doesn't actually include batteries.

I have two questions.

1. Is this feasible? Can one fit a Presta valve on a pump such as the one pictured? A Presta valve is not listed among its paraphernalia. (I'm assuming the Schrader valve is identical on cars and bikes.)

The upper limit of pressure of the pump pictured is 120psi. This matches the needed pressure for the road bike tire. But it would have been nice if the pump were to exceed it ever so slightly.

2. Would a pump rated at 120psi be sufficient for a tire needing 120psi? Or, conversely, is it a big deal if a road bike tire is inflated at only 115psi (because the upper limit is a theoretical, not actual, upper limit)?

Answer 1

There's a lot going on in this question!

The pump pictured seems to be intended for car tyres which can be considered high volume, low pressure and feature Schrader valves.

A 120 psi road bike tyre can be considered low volume, high pressure, and will typically take a Presta valve to suit the narrow rim's smaller valve hole. You can get adapters for pumping up your road bike tyre, but a cycling specific pump won't need this.

That said, 120 psi for a road bike tyre is considered excessive these days, it should be tailored to your weight and 100 psi is a bit of a ceiling for optimal rolling resistance (fashion alert). So its certainly no big deal if you only hit 115 psi, but I would be sceptical of the pump getting close to its maximum rating. I imagine your portable hand pump is rated 100+ psi and probably hard work to get even close, hence looking for an alternative.

By far the best thing to do is do like all the other cyclists who have solved this problem already and buy a quality, cycling specific 'track pump', not a car specific pump. For a road tyre it takes about the same time (# of strokes) to inflate even up to 120 psi, because of the low volume. It actually takes (me) longer to inflate a large volume (26x2.35) mountain bike tyre up to pressure at 30 psi!

The upper limit of a bicycle tyre is the limit below which the manufacturer promises the tyre will not explode off the rim while you cycle along. Most riders should use less than the maximum for comfort and rolling efficiency; generally only riders at the heaviest end of the design weight will need to inflate their tyres to the maximum.

Answer 2

Buy a floor pump, also known as a track pump, instead of an automotive accessory.

A track pump will take about the same time to top up your tires as a small car compressor, and has an advantage of not needing electricity at all.

You still need the on-bike pump for punctures while riding, but in the garage at home a track pump works very well. I ended up carrying a smaller track pump on my bike instead of a minipump.

Do get one with a gauge - doesn't matter if its analogue or digital but estimating tyre pressure by squeeze isn't ideal. A track pump will last you decades, where the small tyre pumps tend to fail in a few years.

Incidentally - I've tried to use my big track pump to add some air to a car tyre, and after 10 minutes I'd raised it from 20 PSI to 22 PSI. If you want to inflate car tyres as well, get both. One pump will not do both jobs well.

My car tyre compressor stalls out at around 70 PSI despite being "rated" for 175 PSI - there is no way it can pump up a road tyre and if I did, would have to finish it off with the hand pump anyway.

Answer 3

I have one of such compressors for car use and of course I have used it on my bikes.

However, I only use it on MTB bikes which I inflate to 40 psi at most. I Do not own a road bike but some slick tires sometimes inflated up to 60 PSI. For MTB tires the compressor is slow enough to allow very accurate pressure control.

The problem I have faced is that as the pressure increases, so does the load on the compressor's motor, in turn the amperage it consumes and that heats the connector. The connector heated enough to blow a thermal fuse in the cigarette lighter socket (I could replace only recently). I is a design flaw in an otherwise very capable compressor.

For Car tires I have no trouble at all since they are used at 33 psi in my case. (Small pickup truck or smaller) For such uses it does heat up, but not as much.

In conclusion, depending on the design of the compressor you acquire, it may not be worth the hassle that it could cause if it damaged your vehicle's socket. Most small cars do not use high pressure tires, and even though the compressor's seller may label it as capable of achieving 150 psi I seriously doubt they actually test the product to such extents (I have seen ones with a depiction of it being used to inflate a tractor tire as tall as an adult, but the construction quality was very cheap, thin cable, lousy connector.)

A proper track pump is way less hassle in practice. There are pumps more suitable for road tires and other are better for MTB, and there are even dual volume pumps. Having the proper valve chuck is faster than dealing with adaptors every time.

A pump can also be used away from the car. I have been to events where I have to park away from the start/finish area or the area where one could perform last minute calibration or puncture repair. I've also have been in the situation where the adjacent cars are too close to allow for the bike to be close enough to operate the compressor on it.

Answer 4

The valve connection is simple, there are adapters for Schrader on Presta, some cycle pumps have these as standard. Your LBS may sell these as extras as well.

Problem would be pressure. Does the pump really deliver the indicated pressure.If the max. pressure delivered by pump is 120psi and your tyre needs more you can't just let it run for a longer time to fill in more air.

The opposite may be more problematic. If your pump delivers a large volume quickly and your tyre only requires 90psi, you may easily over-inflate it because when stopping the pump there is always a delay. If there is a pressure activated switch to turn off the pump at a preset, is that one accurate and consistent. So you'd need a precise gauge anyway.

A track pump with a manometer, activated by muscle power is the better solution for cycle tyres. The pressure is easier to control and the required volume of air is small enough not to call for a motor-driven pump. A further advantage is that the possible pressure is often higher than 120psi.

However, if you use tubeless tyres you may need a more sophisticated hand pump, one with a storage tank that is brought to pressure prior to inflating the tyre. It is then connected to the valve and the air is released to the tyre in one explosive go to seat the tyre bead in the rim.

Answer 5

The most important reason why you do not want to use an electric pump but must use a manual (track or handheld) pump is the risk of damaging your tire.

Calvin Jones at Park Tool explains it here.

An electric pump will inject air too fast for you to have a chance to inspect whether the bead seat line maintains a constant distance from the rim.

If you miss a spot, you take the risk of scuffing the wall of your tire.

To avoid this, you spray soapy water. CJ@PT explains it here.

Even if it's a fatbike tire. As others have pointed out, at the low pressure of fatbike (and MTB) tires, it doesn't take that many pumps with a track pump.

Once your tire is correctly installed, there is no reason not to use an electric pump, but there is little reason to bother. The air loss during a week of riding takes too few manual pumps anyway.

Answer 6

There are Presta to Schrader converters. You should buy one with O-ring (the ones without O-ring are crappy: they leak air). they allow Schrader pumps to be used on Presta tubes.

As for the powered car tire inflator, maybe it will work, maybe not. The key is maximum pressure. The volume in road bike tires is low, so not much inflation heat will be created by a pump that fully fills a road bike tube. Therefore the powered car tire inflator won't overheat.

However, not all car tire inflators are intended for high pressure tires. If the inflator is intended for passenger cars only, it may be limited to 4-5 bar as no passenger car has higher pressures (usually the spare donut tire is the only in a car that may require close to 5 bar). If the inflator is a general purpose tool, intended for all kinds of vehicles, then yes, there are motor vehicle tires that should be pumped to over 100psi / 7bar. So a general purpose tool, intended for all kinds of motor vehicles, is probably able to pump road bike tires.

I won't recommend such an inflator, however. Car tires are pumped with powered inflators because there's a lot of volume and it's a lot of work to get them to even the 2-3 bar pressure they usually have. However, bike tires are so low volume that getting them to 7-8 bar is no effort at all with a proper floor pump.

So as has been already stated, you should buy a floor pump (also called track pump). The best have both Schrader and Presta valve fittings. If you also have a car, you might want to buy the powered inflator in addition to the floor pump. A good bike tool is not a good car tool and vice versa.

For road bikes, buy widest tire you can fit. Maybe it's 32mm, if so you should use one. 85-90psi is plenty for 32mm. Maybe it's 28mm, if so you should use one. 100psi is plenty for 28mm. Unfortunately, there are still road bikes that take no more than 23mm tires. If so you're screwed. 23mm tires do absolutely require 120psi, anything below will pinch flat instantly unless you are a featherweight rider.

Answer 7

Regarding the inflator - I find the schrader-presta adapters leak. This may confuse the electronics and fail to achieve high pressure. Inflators are noisy slow and unreliable too.

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It's an ancient bike myth than schrader valves, used in trucks and aircraft , are low pressure, and not up to the more demanding application of a push bike. The only benefit of presta is narrowness; schrader is too big a hole for narrow rims. Now that road rims are wide we should move to schrader, but it will never happen because roadies would consider it beneath them.

"Track" (make it sound glamorous) pumps are cheap, effective, quick, and reliable.