37431A/37625 Tapered Roller Bearing - Manufacturer comparison

Firstly, if you have come here wanting to buy an 37431A/37625 online then follow this link. This page contains information about the bearing but isn’t the product page for it.

Here, we’re going to be looking at the differences between tapered roller bearing manufacturers for the 37431A/37625 bearing.

The manufacturers that we are going to look at today are Timken, SKF, NTN, NSK and Koyo who are all premium OEM bearing manufacturers and we’re going to look and see whether there are any differences between the manufacturers for this bearing.

37431A/37625 Part numbering

Firstly, let’s look at the part numbering system used.

In the bearing industry this item is commonly known as an 37431A/37625 which comes from the fact that the part number for the inner of the bearing or “the cone” is 37431A and part number for the outer of the bearing or “the cup” is 37625. For this inch sized tapered roller bearing the cone part number usually comes first followed by a “/” and then followed by the cup part number.

The 37431A cone for example could fit not just with an 37625 cup but could fit with a 37625RB cup making the complete part number 37431A/37625RB.

As you can see from the table below most manufacturers have slight variations in how they list their part numbers.

Timken Part Number

37431A - 37625

SKF Part Number


NTN Part Number


NSK Part Number

Not listed

Koyo Part Number



Timken separate their cone and cup part numbers and use a “ – “ to separate them.
SKF shorten the cup part number after the / as the two first numbers are common to the cup and cone. This format is especially common in the bearing distributor market where shortening the part number in this way helps to improve speed. When enquiring for this bearing on the phone for example, a customer might say. “Can you quote me with an 37431A with a 625”. The 625 being easier to say than 37625.They also prefix their part number with PER. Which denotes that the bearing is manufactured by PEER bearings under the PEER brand which is a subsidiary company of SKF. If you ordered this bearing it would be marked with PEER rather than SKF.
NTN list theirs with a 4T- at the beginning. This extra part numbering just means that the bearing is made with a special grade of case hardened bearing steel.
Koyo have a completely different part numbering structure for this item when compared to the other manufacturers. It’s not known why they have chosen to do this but it is common practice amongst manufacturers on some items to do this.

This type of different part numbering practice is common place across all types of bearings, quite often only experience can assist you in knowing how to get from the part number of one manufacturer to the part number of another.

So what else is different about the 37431A/37625 bearing between these manufacturers ? Well you might think that they should all weigh the same because they are meant to be the same part. That isn’t however the case.

37431A/37625 Mass

The table below shows the mass catalogued from each of the manufacturer’s. As you can see there is only a small spread in terms of the mass between different manufacturers. The mass for the SKF 37431A/37625 is missing below as that wasn’t available on their online catalogue.

Timken Mass

1.30 Kg

SKF Mass

Not listed

NTN Mass

1.32 Kg

Koyo Mass

1.337 Kg


Does this mean that a Timken 37431A/37625 is inferior to a Koyo 37431A/37625 because it weighs less ? That’s not really how bearings work. There are many more important factors at play including the precision level and finish of the component parts and the quality of the materials that they are manufactured from. In fact, Timken were the original company to make tapered roller bearings, it is their flagship product and something that they are recognized for around the world as producing with enviable quality levels. They are trusted globally amongst OEM’s and are often the first choice when it comes to tapered roller bearing selection. With the catalogued mass it’s quite feasible that the catalogue mass are computer generated rather than being actually weighed from a real component. Alternatively it’s possible that some manufacturers calculate their mass without packaging and some manufacturers calculate their weight with packaging. What we’re saying is take the catalogued mass with a pinch of salt. There are bearing series where the mass do play a part in the quality but amongst premium manufacturers like these, especially with tapered roller bearings the weight is not a factor in whose bearing is best.

37431A/37625 Load Ratings

What about load ratings ? Surely if one of the manufacturers has a higher load rating for the 37431A/37625 bearing then that makes it better the others right ? As always with bearings it’s not quite that simple. Looking at the table below it looks like Timken is streets ahead and that SKF and are lagging behind.

Static Load Rating

Dynamic Load Rating


179 kN

137 kN


157 kN

97.8 kN


166 kN

114 kN


Not listed

Not listed


Well, most load ratings are calculate load ratings not tested load ratings. It’s basically taking information about the bearing, running it through a formula and the load ratings in the catalogue are a result of that calculation. That’s not to say there isn’t anything in it. Timken as I’ve mentioned before are market leads for tapered roller bearings so it certainly wouldn’t be surprising if they actually had the higher load ratings in real life but we just cannot take the catalogued figures in isolation and say one bearing is better than another.

You will be pleased to hear that one thing that does stay the same between all manufacturers is that the dimensions stay the same. Tapered roller bearings are produced to ISO 355, JIS B 1512 and ABMA standards which define the dimensions and tolerances for different types of bearings so whilst the internal geometry of the bearings might differ between manufacturers, when it comes to the overall dimensions they remain the same.

As we develop the site further we will look to put the 37431A/37625 bearings from each of the manufacturers on accelerated bench tests at various loads and speeds so that we can truly see whose bearings outperform the others. 

We hope that you have found this information useful. If you think it would be beneficial for us to write on another bearing related topic then please contact us and we will add it to our workflow. We are keen to make sure that we become a knowledge resource for all things bearing related and bridge that gap of requiring industry experience to navigate the minefield that is bearings.

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